Reduced Wall Thickness Research Articles

Application of Hougaard stochastic model for flow-accelerated corrosion wall thinning in an orifice

In this paper, Hougaard process stochastic degradation model has been used for the prediction of wall thickness reduction in pipes between two consecutive in-service inspections. Experimental data on FAC in gypsum orifice, from the literature, were used. There were nine locations downstream of the orifice where the wear of wall was measured at 1 h, 2 h, 3.5 h, 4.5 h, 6.5 h, 9.6 and 13 h into the experiment. The predicted wall thickness reduction compared well with the experimental wall thickness reduction from 9.6 h to 13 h.

Hot Gas Forming of Aluminum Alloy Tubes Using Flame Heating

Hot metal gas forming (HMGF) is a desirable way for the automotive industry to produce complex metallic parts with poor formability, such as aluminum alloys. A simple hot gas forming method was developed to form aluminum alloy tubes using flame heating. An aluminum alloy tube was heated by a flame torch while the tube was rotated and compressed using a lathe machine and simultaneously pressurized with a constant air pressure. The effects of the internal pressure and axial feeding on expansion and wall thickness distribution were examined. The results showed that the proposed gas forming method was effective for forming aluminum alloy tubes. It was also indicated that axial feeding is a vital parameter to prevent reductions in wall thickness by supplying the material flow during the forming process.

Optimizing the Gamma Process.

This article will discuss opportunities to improve the efficiency of cobalt-60 (Co-60) utilization within a gamma irradiator. It will show how redistributing the Co-60 within the source rack may lead to improved throughput or dose uniformity within a product. It presents examples of modifications to the equipment within the source pass; these include reduction in the carrier wall thickness and changes to the product stack size. It will discuss the process of scheduling and present ideas of how to optimize both the order of the products and transitions between the products to maximize process efficiencies.

P318Positive left ventricular remodeling after TAVI assessed by high resolution electrocardiography

Abstract Introduction Transcatheter aortic valve replacement (TAVI) is a novel treatment method for sever aortic stenosis that has a positive impact on reverse left ventricular (LV) remodeling. The morphology and function of the LV can be assessed by transthoracic echocardiography (TTE) and high resolution electrocardiography (HR-ECG). Purpose The purpose of our study was to investigate whether morphological and functional myocardial changes after TAVI seen on TTE can be tracked by advanced ECG parameters using HR-ECG. Methods Consecutive TAVI patients with transfemoral approach were included in this pilot prospective study. A 5 minute HR-ECG and TTE were performed before and one year after TAVI. Spatial QRS vector amplitude (3D_QRSm), total 12-lead QRS amplitude (12leadV), spatial QRS-T angle (QRST_aM) and spatial ventricular gradient (SVG) were measured using HR-ECG and interventricular septum diastolic diameter (IVSd), left posterior wall diameter (LVPWd), left ventricular ejection fraction (LVEF) and tissue Doppler peak septal systolic velocity (Sm) were obtained by TTE. Student"s test was used for pairs to analyze the differences in sets of variables before and after TAVI and Pearson correlation coefficient to analyze the relationship between TTE and HR-ECG parameters. Results 15 patients (5 male; 33.3%) were included in the study. At one year follow-up we found statistically significant reduction in LV wall thickness and increase in LVEF (61.6 ± 6.50 % vs. 66.9 ± 7.84 %, p = 0.043). In the subgroup with narrow QRS (8 patients), we found a statistically significant correlation between change of left posterior wall thickness (deltaLVPW) and spatial QRS vector amplitude (delta3D_QRSm) (r = 0.795; p = 0.018), and between change of left ventricular ejection fraction (deltaLVEF) and spatial QRS-T angle (deltaQRST_aM) (r = 0.604; p = 0.038). No significant correlations were found in the subgroup of patients with wide QRS complex. Conclusions Our pilot study showed that morphological and functional myocardial changes after TAVI in patients with narrow QRS complex can be followed with advanced ECG parameters using HR-ECG. HR-ECG could prove to be a simple and inexpensive method of follow-up after TAVI in patients with narrow QRS. To ascertain the usefulness and reliability of HR-ECG, a study on a larger number of patients would be required.

Optimization of spinning process parameters for the large-diameter thin-walled cylinder based on the drum shape

Thinning spinning has the advantage of enhancing the performance of a product, and it is an effective method for manufacturing large-diameter ultrathin cylindrical parts. However, the rigidity of a large-diameter ultrathin wall cylinder is poor, the spinning process and forming quality are sensitive to the process parameters, and the drum-shaped result of the spinning process is prone to instability, which can cause the spinning process to be unbalanced. Therefore, it is a great challenge to select the appropriate process parameters for achieving the long-range stable spinning of large-diameter ultrathin wall cylinders. Based on the analysis of the thin-walled cylinder spinning mechanism, this study analyzed the effects of key process parameters on the drum shape of a C-276 thin-walled cylinder spinning process by serial experiments. The results of serialization experiments show that the thinning rate has a great influence on the spinning process state, the feed rate is secondary, and the speed has the least influence. On the basis of experimental analysis, the optimized process parameters of thin-walled cylinder spinning are obtained by using the support vector machine method: the wall thickness reduction rate cannot exceed 45% in single-pass spinning; 30~40% is a reasonable choice interval; the feed rate can range from 0.8 to 1.0 mm/r; and the rotation speed can range from 80 to 100 r/min. Finally, a comparative experiment and stability test of thin-walled cylinder thinning spinning over a long range is carried out, which verifies that the optimized spinning parameters can be used for the long-range stable spinning of large-diameter ultrathin cylinder parts.

Plastic intensity reduction using thermally insulating coatings for injection molds

The use of plastics in today's world is still increasing despite its enormous burden for environmental sustainability. The urge to reduce plastics impact is driving the development of novel technological solutions. The high viscosity of thermoplastic polymer melts often leads to the design of oversized plastic parts having wall thickness higher than structural requirements. This work proposes a novel approach to wall thickness reduction, exploiting the thermally insulating effect of mold coatings. Four different mold coatings were characterized using inline rheological testing carried out on a PET using a slit-die open mold. The thermal boundary condition of a numerical model was calibrated by fitting the numerical to experimental pressure values. The thickness reduction associated with the use of a specific coating was then quantified for a case study geometry using the calibrated model. The results indicated that it is possible to reduce the thickness of the part by 12%, leading to material consumption and cycle time reduction of 8% and 22%, respectively.

Effects of fish origin probiotics on growth performance, immune response and intestinal health of shrimp (Litopenaeus vannamei) fed diets with fish meal partially replaced by soybean meal

This study was conducted to evaluate the application of four fish origin probiotics to relieve the side effects induced by SBM in shrimp. Shrimps were fed with high fish meal diet (C0, positive control containing 500 g/kg FM and 0 g/kg SBM), low fish meal diet (C, control containing 250 g/kg FM and 340 g/kg SBM) or the control diet (C) supplemented, respectively, with 1.0 × 10⁸ CFU/g Bacillus pumilus SE5 (T1), Psychrobacter sp. SE6 (T2), Enterococcus faecium MM4 (T3) or Bacillus claussi DE5 (T4). After 6 weeks of feeding, the growth performance, hepatopancreatic digestive enzymes, intestinal histological structure and immune parameters were determined. The results showed that compared with high FM group (C0), significantly lower WGR and SGR as well as higher FCR were observed in the low FM group (C) (p < .05). Compared with the control, significantly lower FCR was observed in treatment T1 (p < .05), but not in treatments T2–T4. Protease, amylase and lipase activities in all the treatments (T1‐T4) were significantly higher than the control (p < .05). GOT and GPT activities in the control were significantly lower than the C0 (p < .05), while higher MDA level was recorded in the control (p < .05). Meanwhile, higher GPT activities were observed in treatments T1‐T4 compared with the control (p < .05). Compared with the C0, lower SOD, ACP and AKP activities were observed in the control. Significantly improved SOD and AKP activities were observed in all probiotic feeding groups compared with the control (p < .05). The control diet led to significant reduction of intestinal wall thickness and villus height compared with the C0 (p < .05), while significantly higher intestinal wall thickness and villus height were exhibited in all the probiotic groups compared with the control (p < .05), except intestinal wall thickness in treatment T3. Thus, these results demonstrated that the four fish origin probiotic strains could relieve the side effects induced by high level of SBM in shrimp, while probiotic B. pumilus SE5 showed the best performance.

Female Mice Are Resistant to Inward Remodeling of Parenchymal Arterioles Observed in Male Mice During Angiotensin II‐Induced Hypertension

Hypertension increases risk of vascular cognitive impairment and dementia (VCID) by impairing the structure and function of cerebral arteries. These arterial changes result in chronic hypoperfusion of the brain parenchyma and, eventually, cognitive impairment. Epidemiological studies suggest a sex difference in development of VCID, with women being protected from its development until late in age. We have previously shown that angiotensin II (AngII)‐hypertension led to inward hypotrophic remodeling and decreased wall stress in the parenchymal arterioles (PAs) of male mice. This PA remodeling in AngII‐hypertension was associated with reduced cerebral perfusion, increased myogenic tone, and cognitive dysfunction. Female mice, however, were protected from memory impairments despite a similar increase in blood pressure and decrease in cerebral perfusion measured by scanning laser Doppler. We hypothesized that AngII‐hypertension in female mice will cause a decrease in cerebral perfusion measured by laser speckle contrast, as well as a decrease in outer diameter, lumen diameter, and wall thickness in the PAs. Sixteen to eighteen‐week‐old female C56BL/6 mice were treated with AngII (1200 ng/kg/min via osmotic mini‐pump) for four weeks. This dose was selected to produce a similar increase in blood pressure to the previously studied male mice. Sham mice served as control. Blood pressure was measured by tail‐cuff plethysmography and pial blood flow was measured. After euthanasia, brains were collected and PAs were isolated and mounted on a pressure myograph for assessment of spontaneous myogenic tone generation and structure. PA structure was assessed by increasing intralumenal pressure from 3mmHg to 120mmHg in 20mmHg increments. Results are presented as means ± SEM and PA data are reported at an intralumenal pressure of 40mmHg (n=5–12). Systolic blood pressure was increased (Sham: 141 ± 7, AngII: 179 ± 7mmHg; p&lt;0.05) and cerebral perfusion was reduced in AngII‐hypertension (Sham: 328 ± 6, AngII: 288 ± 11 perfusion units; p&lt;0.05). AngII infusion slightly decreased lumen (Sham: 49 ± 3, AngII: 42 ± 4μm; p=0.17) and outer (Sham: 57 ± 4, AngII: 48 ± 4μm; p=0.11) diameters, although not significantly. AngII‐hypertension reduced wall thickness (Sham: 4 ± 0.3, AngII: 3 ± 0.2μm; p&lt;0.05) and wall area (Sham: 691 ± 83, AngII: 441 ± 52μm2; p&lt;0.05). PAs from female mice did not show reductions in wall stress (Sham: 241.8 ± 19, AngII: 268 ± 20dynes/cm2; p&gt;0.05) or generate more myogenic tone in response to hypertension (Sham: 27 ± 4, AngII: 22 ± 2%; p&gt;0.05). While AngII‐hypertension resulted in reductions in lumen diameter, outer diameter, wall thickness, and wall stress in the PAs of male mice, PAs of female mice had only reduced wall thickness with modest reductions in lumen and outer diameters. Preliminary data suggest that females may be resistant to inward PA remodeling during AngII‐hypertension, despite similar reductions in cerebral blood flow as male mice. This potential protection of the cerebrovascular structure and myogenic tone generation could explain the absence of cognitive dysfunction in response to hypertension in female mice.Support or Funding Information5T32GM092715‐14

Multi-objective optimization of western bentonite (Al2H2Na2O13Si4)-blended green sand casting process parameters to improve mould quality

The quality of the mould in the green sand casting process plays a vital role in achieving good quality castings. In this research work, the mould properties permeability and hardness are focused on to improve the quality of the mould. These properties are improved by optimizing the process parameters such as degrees of ramming, mould wall thickness, and weight percentage of western bentonite using Taguchi-based grey relational analysis. The optimal level of these process parameters is experimentally validated by producing castings in a modern jobbing foundry. In the validation experiments, the moulds are produced with nominal hardness (92) and the mould wall thickness is reduced by creating cavities for storage of gases at a distance of 30 mm from the mould cavity. An interesting result found is that the nominal mould hardness and reduced wall thickness improve the quality of the mould by increasing the permeability value from 80 to 120. The improved mould quality reduces the mould-related casting rejection rate in pressure plate casting from 40% to 30%.

The therapeutic impact of human neonatal BMSC in a right ventricular pressure overload model in mice

ObjectiveTo determine the impact of donor age on the therapeutic effect of bone marrow-derived mesenchymal stem cells (BMSCs) in treating adverse remodeling as the result of right ventricle (RV) pressure overload.MethodsBMSCs were isolated from neonatal (< 1 month), infant (1 month to 1 year), and young children (1 year to 5 years) and were compared in their migration potential, surface marker expression, VEGF secretion, and matrix metalloprotein (MMP) 9 expression. Four-week-old male C57 mice underwent pulmonary artery banding and randomized to treatment and untreated control groups. During the surgery, BMSCs were administered to the mice by intramyocardial injection into the RV free wall. Four weeks later, RV function and tissue were analyzed by echocardiography, histology, and quantitative real-time polymerase chain reaction.ResultsHuman neonatal BMSCs demonstrated the greatest migration capacity and secretion of vascular endothelial growth factor but no difference in expression of surface markers. Neonate BMSCs administration resulted in increasing expression of VEGF, a significant reduction in RV wall thickness, and internal diameter in mice after PA banding. These beneficial effects were probably associated with paracrine secretion as no cardiomyocyte transdifferentiation was observed.ConclusionsHuman BMSCs from different age groups have different characteristics, and the youngest BMSCs may favorably impact the application of stem cell-based therapy to alleviate adverse RV remodeling induced by pressure overload.

Clopidogrel or prasugrel reduces mortality and lessens cardiovascular damage from acute myocardial infarction in hypercholesterolemic male rats

AimsHypercholesterolemia is a hazard for increasing susceptibility of the heart to myocardial infarction (MI) by inducing platelet hyperaggregability. Clopidogrel and prasugrel have documented cardioprotective effects in clinical studies. Herein, we investigated whether clopidogrel and prasugrel could protect against isoproterenol-induced acute MI (A-MI) under hypercholesterolemic conditions in rats. Main methodsDietary hypercholesterolemic rats were subjected to acute doses of isoproterenol. Serum lipids, inflammatory markers, aortic endothelin1 and endothelial nitric oxide synthase (eNOS) mRNAs expression and immunexpression of BCL2 were determined. Key findingsHypercholesterolemic rats showed infiltration of inflammatory cells and reduction in aortic wall thickness, deposition of fibrous tissue between cardiac muscle fibers. Protective doses of prasugrel or clopidogrel for 28 days before A-MI increased survival, amended the ECG parameters -including ST segment elevation- and improved the histopathological picture in hypercholesterolemic rats. This was coupled with reductions in platelet aggregation, creatine kinase-MB activity, endothelin 1, systemic inflammation and cardiac lipid peroxidation and increment in aortic eNOS expression. Clopidogrel and prasugrel groups showed enhanced BCL2 expression in cardiac fibers and aortic wall. SignificancePrasugrel and clopidogrel protected against A-MI via anti-aggregatory and anti-inflammatory effects. These results add to the value of these drugs in correcting cardiovascular dysfunction in patients vulnerable to A-MI after confirmation by appropriate human studies.

Application of pre-deformation rolling in the welding heat-affected zone of tailor-welded blanks formed by deep-drawing process

Excessive wall thickness reduction occurs in the welding heat-affected zone (HAZ) of tailor-welded blanks (TWBs) during the deep-drawing process. The pre-deformation rolling (PDR) for welding HAZ was introduced in this study. The double-ellipsoidal heat source mechanical model was used to simulate welding, PDR, and plastic deformation processes of standard tensile specimens and large-size TWBs. Results show the uniform distribution of equivalent strain and wall thickness of the specimens with 4 % PDR reduction in the HAZ after uniaxial tensile deformation under the same elongation. Thus, the 4 % rolling reduction not only improves the material strength of the HAZ but also ensures good ductility. The optimum 4 % PDR parameters are applied to the deep-drawing process of large TWB container heads. The wall thickness of the HAZ and the base material are uniformly reduced after the deep drawing of the TWB because 4 % PDR improved the plastic deformation capability of the HAZ. Finally, the experimental study on the deep drawing forming and microstructure of large TWBs is conducted. Compared with the HAZ without PDR, the HAZ wall thickness of the deep-drawing forming head with 4 % PDR reduction in the HAZ is increased from 3.98 mm to 4.25 m. Moreover, the grains are fine and uniform similar to those of the base material. Furthermore, the distribution of hardness values in each area of the deep-drawing formed head is uniform.

Influences of feed rate and wall thickness reduction on the microstructures of thin-walled Hastelloy C-276 cylindrical parts during staggered spinning

Staggered spinning is an advanced method to manufacture thin-walled cylindrical parts. The microstructure evolution, which dominantly influences the overall performance, is very complex during the staggered spinning of Ni-based cylinder. In this work, the influences of feed rate and wall thickness reduction on the microstructures of a thin-walled Hastelloy C-276 cylinder during staggered spinning are investigated. It is found that the deformation of parts is highly inhomogeneous, and the microstructures are sensitive to the feed rate and wall thickness reduction during the staggered spinning. When the wall thickness reduction is small, the single slip is responsible for the deformation of grains. The deformation mechanism changes from single slip to cross slip with the increase of wall thickness reduction. Moreover, the uniform deformation of thin-walled Hastelloy C-276 cylinder can be obtained when the feed rate is about 0.8 mm/r or the wall thickness reduction is about 44.1%. These findings provide guidance for controlling the microstructures of thin-walled cylindrical parts during staggered spinning.

Electromagnetic Force Distribution and Wall Thickness Reduction of Three-Coil Electromagnetic Tube Bulging With Axial Compression

In the conventional electromagnetic tube expansion, tube wall thickness tends to decrease significantly while the workpiece is expanded. This paper is aimed at introducing a new technique using three-coil electromagnetic tube bulging with axial compression as an innovative solution for this issue. To validate the feasibility of the proposed technique and investigate the electromagnetic force distribution along the workpiece, COMSOL software is used to construct a detailed finite element analysis model for the proposed electromagnetic coupling model. Results show that the ratio of the axial and the radial electromagnetic forces increases linearly with the increase of the height and the outer diameter of the top and bottom coils. Furthermore, the tube deformation profile and the wall thickness are compared with two different coil structures. Comparison analysis reveals that for the same axial to radial electromagnetic forces ratio, the effect of prohibiting the wall thickness reduction using different coil structures is quite similar. The new method is expected to have a good potential in enhancing the tube-forming performance.

Efficacy of tolterodine in children with overactive bladder.

Aim:Tolterodine is an anticholinergic drug used for the treatment of overactive bladder. We evaluated the effects of tolterodine on clinical symptoms and compared its efficacy with that of oxybutynin in terms of bladder capacity, bladder wall thickness, and post-void residual volume in children with overactive bladder.Material and Methods:Twenty-six patients who were treated with tolterodine for overactive bladder (20 girls, mean age 8.0±2.2 years) were evaluated retrospectively. Twenty patients with overactive bladder who had undergone oxybutynin treatment (15 girls, mean age 7.6±1.8 years) served as the control group. Dysfunctional voiding symptom scoring was used to evaluate the clinical response to tolterodine. To investigate the effect of treatment on the bladder, ultrasonographic data at baseline and the third month were compared with the oxybutynin group.Results:The dysfunctional voiding symptom scores significantly decreased after the third month of tolterodine treatment (p<0.001). Bladder capacity significantly increased (p<0.001), and filled bladder wall thickness decreased (p=0.007); however, post-void residual volumes significantly increased (p<0.001) at the third month. No serious adverse effects were recorded during tolterodine treatment. The increase in bladder capacity at the third month in the tolterodine group was similar to that in the oxybutynin group (p=0.77), but the decrease in filled bladder wall thickness was significantly greater in the tolterodine group (p=0.019).Conclusion:Tolterodine remarkably ameliorates the clinical symptoms of overactive bladder in a short time, and seems to be as effective as oxybutynin for the treatment of overactive bladder in children. Its effect on reduction of bladder wall thickness appears to be superior to that of oxybutynin.

Tube Electromagnetic Free Bulging Based on Internal Negative-External Positive Three-Coil System

Controlling the direction and profile of the electromagnetic force (EMF) is a key of improving the tube axial-uniformity and wall thickness during the electromagnetic forming process. In this regard, this article proposes a new tube electromagnetic-bulging topology using internal negative-external positive three-coil system. This structure is aimed at realizing effective bidirectional loading of axial and radial EMFs on the tube. An electromagnetic-structure coupling two-dimensional model is proposed to study the effect of the coil structure on the EF profile, bulging profile and the tube wall-thickness. The performance of the proposed method is compared with the traditional method through several performance metrics that include the electromagnetic force distribution cloud map, the tube bulging uniformity and its wall thickness. Numerical simulation results show that by changing the coil structure, the radial EMF profile can be effectively enhanced, and the free bulging contour of the tube can be further regulated. The additional axial EMF due to the proposed structure can promote the axial-flow of the material, thereby suppressing the reduction in the tube wall-thickness which is unavoidable using the traditional method. In comparison to the traditional single-coil system bulging, the maximum axial uniformity range of the tube is increased from 6.5mm to 35.2mm, and the wall thickness of the most severely thinned area is increased from 1.43mm to 1.77mm which verifies the effectiveness of the proposed method.

Numerical and experimental evaluation of an alternative mechanism for wall thickness variations of hollow profiles applying a porthole die

The cross sections of conventionally extruded profiles remain constant along the length of the extrudates due to application of static, rigid dies. The profile cross section is dimensioned according to the expected loads applied during technical application. Mostly, the loads are not distributed homogeneously upon the length of a product. Thus, locally over-dimensioned profile areas are the result. In order to optimize the profile design and therefore obtain lighter products, load adapted tailored profiles should be manufactured. In this paper a mechanism for wall thickness variations of lightweight hollow profiles was investigated by finite element analysis (FEA) and experimental extrusion trials. The principle for manufacturing wall thickness variations is based on application of bending elements which work as bearing channel at the porthole die. Their deflection in direction of the die bearing would lead to wall thickness reductions. An increase of the wall thicknesses should be achieved by a deflection of the bending elements back into direction of their initial position due to the normal pressure of the flowing aluminum billet material. FEA of the material flow during extrusion was conducted in order to investigate the principle feasibility of the mechanism. The force requirements for wall thickness variations were also gained from the numeric simulations on the one hand. The force necessary for the deflection of the bending elements was also determined in an experimental test setup. The extrusion tryouts applying the developed mechanism revealed that the force of the hydraulic drive was successfully transmitted onto the moveable segments inside of the porthole die. Although subsequent to the extrusion experiments variations of the hollow profile wall thicknesses were observed, it was found out that they were not induced by the developed mechanism as intended. Instead, aluminum billet material filled even smallest voids and gaps inside of the mechanism causing deflection and failure of different components that effected the development of the wall thickness.

Fracture resistance after implantoplasty in three implant-abutment connection designs.

Background To assess the effect of implantoplasty and implant-abutment design on the fracture resistance and macroscopic morphology of narrow-diameter (3.5 mm) dental implants. Material and Methods Screw-shaped titanium dental implants (n = 48) were studied in vitro. Three groups (n = 16) were established, based on implant-abutment connection type: external hexagon, internal hexagon and conical. Eight implants from each group were subjected to an implantoplasty procedure; the remaining 8 implants served as controls. Implant wall thickness was recorded. All samples were subjected to a static strength test. Results The mean wall thickness reductions varied between 106.46 and 153.75 µm. The mean fracture strengths for the control and test groups were, respectively, 1211.90±89.95 N and 873.11±92.37 N in the external hexagon implants; 918.41±97.19 N and 661.29±58.03 N in the internal hexagon implants; and 1058.67±114.05 N and 747.32±90.05 N in the conical connection implants. Implant wall thickness and fracture resistance (P < 0.001) showed a positive correlation. Fracture strength was influenced by both implantoplasty (P < 0.001) and connection type (P < 0.001). Conclusions Implantoplasty in diameter-reduced implants decreases implant wall thickness and fracture resistance, and varies depending on the implant-abutment connection. Internal hexagon and conical connection implants seem to be more prone to fracture after implantoplasty. Key words:Dental implants, narrow diameter, implant connection, peri-implantitis, implantoplasty, fracture strength.

Parametric Simulation Analysis of the Electromagnetic Force Distribution and Formability of Tube Electromagnetic Bulging Based on Auxiliary Coil

Tube electromagnetic bulging has been given much attention due to its superior advantages in the field of light alloy processing. However, the conventional tube electromagnetic bulging process exhibits some critical issues that restrict its wide industrial applications. This includes non-uniform axial deformation and poor forming performance such as wall thickness thinning. This article proposes a cost-effective solution for such issues through simultaneous radial and axial electromagnetic force loading using an auxiliary driving coil. In this regard, the influence of the auxiliary coil geometrical parameters on the electromagnetic force distribution and tube forming performance is investigated using electromagnetic-structure coupling model of the bulging process. The robustness of the new proposed method is validated by comparing its electromagnetic force distribution and tube forming performance with the traditional cylindrical coil method, currently used by industry practice. Numerical results show that the introduction of the auxiliary coil may effectively weaken the radial electromagnetic force at the end of the tube and solve the uneven axial deformation issue. Based on the obtained results, the maximum uniform deformation area is increased from 6.9mm to 35.1mm. The tube relative wall thinning issue is reduced and the relative wall thickness reduction of the pipe is found to be 0.01661. The axial electromagnetic force can be further improved by adjusting the geometrical parameters of the coil and the proposed electromagnetic bulging can effectively increase the uniform deformation range of the tube.

ВОЗМОЖНОСТИ УМЕНЬШЕНИЯ ПОПЕРЕЧНОЙ РАЗНОСТЕННОСТИ ХОЛОДНОКАТАНЫХ ТРУБ ИЗ СПЛАВОВ НА ОСНОВЕ ТИТАНА

Цель. Целью исследований маршрутов производства и твердости труб было получение новых научно-практических данных о возможности уменьшения поперечной разностенности холоднокатанных труб из сплавов на основе титана для дальнейших рекомендации о модернизации маршрутов прокатки труб.Методика. Исследованы и обобщены данные, характеризующие химический состав и механические свойства труб, изготовленных из различных сплавов на основе титана. Для труб из сплава ПТ-1М проведен эксперимент по исследованию твердости, что дополнило ранее обобщенные данные о сплавах. Исследование твердости труб выполнялось путем лабораторных исследований образцов труб различной толщины из сплава ПТ-1М в недеформированном состоянии. Для построения графика соотношение предела прочности и твердости НВ сплавов на основе титана были использованы как табличные показатели, так и результаты собственных исследований. Исследование проектирования маршрутов прокатки труб из сплавов на основе титана выполнялось путем сопоставления рассчитанных параметров в соответствии с необходимыми технологическими процедурами.Результаты. Исследовано соотношение предела прочности и твердости НВ, а также построен график соотношения для сплавов на основе титана, который включает данные о таких сплавах как ВТ1-00, ПТ-7М, АТ3 и ПТ-1М, ОТ4-0, ВТ9 и др. Теоретически и экспериментально показано, что абсолютная разностенность стенки холоднокатаных труб из сплавов на основе титана обратно пропорционально зависит от степени относительной деформации при холодной прокатке. Рассмотрены подходы, применяемые для проектирования маршрутов прокатки труб из сплавов на основе титана. Проведено сравнение известного маршрута прокатки, а также новых разработанных маршрутов прокатки. Прогнозирование изменения разностенности с использованием развитого метода показало, что у новых маршрутов прогнозируемый уровень разностенности ниже на ~ 30 % в сравнении с существующим.Научная новизна. Дополнены данные о твердости труб, изготавливаемых их сплава ПТ-1М. Расширены сведения зависимости твердости труб от предела прочности для группы титановых сплавов. Показано практическое применение предложенного метода прогнозирования поперечной разностенности.Практическая ценность. По результатам исследований рекомендованы подходы к выбору и разработке маршрутов прокатки при производстве холоднокатаных труб из сплавов на основе титана, обеспечивающих повышение их точности. Представлены формулы, пригодные для экспресс-прогноза точности труб в зависимости от степени суммарной деформации при холодной прокатке.