Study on the clogging mechanism of punching screen in sand control by the punching structure parameters

As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well.However,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen.To explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined method.According to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was analyzed.The results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of clogging.In the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit.In the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the opening.In the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage rate.The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen and sand prevention selection.

Forming and Springback Prediction of Strips Under Multi-square Punch Concave Forming Process Considering Partial-unloading Effects

To further investigate the forming mechanism and springback characteristics of strips under multi-square punch forming (MSPF) considering partial-unloading effects, a series of concave form ing tests of strips are conducted on the MSPF machine. This paper aims to reveal the physical mecha nism of the elastic-plastic deformation in the MSPF process considering the effect of the forming ap proaches, and derive appropriate mathematical interpretations. The theoretical model is firstly estab lished to analyse the concave forming mechanism and springback characteristics of the strip, and its accuracy is then validated by experimental data. The forming history and load evolutions are depicted to explore the required forming capacity through the proposed analytical method. Besides, the paramet ric studies are carried out to discuss their effects on the springback of the strip. The results suggest that the deformation paths of the strip are influenced by the forming approach, and the springback of the strip in convex forming is larger than that in concave forming.

A Study on the Problem of Employee Punch Card Substitution in Enterprise Management:The Case of Jingdong Enterprise

With economic progress and the continuous advancement of science and technology,the issue of employees substituting punch cards has gradually become a significant challenge in enterprise management.The purpose of this paper is to discuss the causes,effects,and countermeasures of the employee punch card phenomenon,with the aim of providing effective management recommendations for Chinese enterprises.In practice,enterprises should flexibly apply the countermeasures proposed in this paper according to their specific circumstances to prevent substitute punch card incidents and improve overall management efficiency.

板柱节点考虑弯剪相关性的受冲切承载力计算方法

对于同时受到竖向荷载和不平衡弯矩作用的板柱节点,目前已有方法大多将不平衡弯矩等效为竖向荷载,从而给出其受冲切承载力计算方法。但该方法所涉及的不平衡弯矩比例系数的计算还存在较大争议,且没有考虑竖向荷载与不平衡弯矩耦合的影响。因此,本文首先通过推导给出仅有竖向荷载作用的板柱节点受冲切承载力计算公式和仅有不平衡弯矩作用的板柱节点受弯承载力计算公式,并与试验结果进行对比,验证了所提公式的合理性。然后基于板柱节点在竖向荷载和不平衡弯矩共同作用下的试验结果,拟合得到板柱节点考虑弯剪相关性的受冲切承载力计算公式。最后对所提计算方法与不同规范计算方法进行对比,结果表明本文计算方法能够更加准确地预测板柱节点受冲切承载力。

Identification of material parameters from punch stretch test

To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identification procedure, the optimization strategy combines finite element method （FEM）, Latin hypercube sampling （LHS）, Kriging model and multi-island genetic algorithm （MIGA）. The proposed approach is used on material parameter identification of aluminium alloy sheet 2D12. The anisotropic yield criterion Hill’90 is discussed. The results show that the Hill’90 anisotropic yield criterion with identified anisotropic material parameters has a good potential in describing the anisotropic behaviours. It provides a way to obtain the material parameters for FE simulations of sheet metal forming.

DP980超高强钢与AA5052铝合金薄板预成形无铆连接实验研究

目的研究预成形无铆连接相关工艺参数对超高强钢与铝合金薄板接头形貌的影响及连接效果。方法采用预成形无铆连接方法,对钢板进行预成形,解决铆接过程中因变形抗力太大导致的接头断裂或互锁量不足问题,同时,提出带有压台结构的铆接凸模,以防止铝合金材料外溢,压实接头,进一步提高铆接质量。选取DP780高强钢、DP980超高强钢和AA5052铝合金薄板为研究对象,以预成形深度、凹模深度以及凸模压台高度为变量,通过各种组合方法进行无铆连接实验,对比分析各工艺参数对DP780/AA5052和DP980/AA5052接头形貌的影响规律,最后采用剪切和剥离强度实验,评价DP980/AA5052预成形无铆连接的可行性与效果。结论接头检测结果表明,随着预成形深度和凹模深度的增大以及压台高度的减小,接头互锁量增大,其中预成形深度影响较大;随着预成形深度和压台高度的减小以及凹模深度的增大,接头颈厚略有增加,其中凹模深度影响较大。由剪切和剥离实验可知,进行剪切实验时,DP780/AA5052接头出现剥离和剪切失效,DP980/AA5052接头皆为剥离失效;进行剥离实验时,2种板材接头都为铝板撕裂失效;对比两者接头剪切强度得到DP980/AA5052接头连接强度高于DP780/AA5052接头的连接强度,验证了超高强钢与铝合金薄板预成形无铆连接的可行性。

Equivalent Doping Transformation Method for Predicting Breakdown Voltage and Peak Field at Breakdown of Epitaxial-Diffused Punch-Through Junction

Based on a new semi empirical analytical method, namely equivalent doping transformation, the breakdown voltage and the peak field of the epitaxial diffused punch through junction have been obtained. The basic principle of this method is introduced and a set of breakdown voltage and peak field plots are provided for the optimum design of the low voltage power devices. It shows that the analytical results coincide with the previous numerical simulation well.

Plasma Nitriding-Assisted Printing of Stainless Steel Punches for Micro-piercing Process

MEMS （micro-electric-mechanical-system） required for miniature, thin mechanical parts as a structural member; e.g., the miniature pumping system consisted of ten to twelve thin metallic plates before joining. At present, those thin shaped sheets were fabricated by the chemical etching. Their geometric inaccuracy as well as long leading time often became an engineering issue. Micro-piercing process was expected to make mass production of thin sheet products with complex and accurate geometry for much shorter leading time once the die for this micro-piercing was built in. In the present paper, a new plasma nitriding-assisted printing was proposed as an automatic production line to fabricate the micro-piercing punch. After preparation of CAD-data of the punch head, its two dimensional geometry was ink-jet printed directly on the AISI420 stainless steel die-substrate. The unprinted surface area was only plasma nitrided at 693 K for 14.4 ks to transform this two dimensional micro-pattern to the three dimensional hardness distribution in the AISI420 substrate. Through the mechanical removal of ink-jet printed area, the flat punch head with sharp edge comers was fabricated in much shorter duration time than the end-milling. SEM-EDX, surface profiling measurement as well as micro-hardness testing were employed to describe each step in the above plasma printing. The thin MEMS stainless steel part with a micro-pendulum as well as three S-letter shaped springs was taken for an example to describe this automatic production procedure of plasma printing from the CAD data mining to the micro-piercing punch finishing.

Henry入路蝶形钢板内固定治疗桡骨远端双柱Die-punch骨折

目的:探讨Henry入路蝶形钢板切开复位内固定治疗桡骨远端双柱Die-punch骨折的临床疗效。方法:选择2018年1月至2021年6月采用Henry手术入路切开复位内固定治疗的26例桡骨远端双柱Die-punch骨折患者,男14例,女12例;年龄20~75(44.2±3.4)岁。观察术后并发症情况,术后12个月采用Gartland-Werley评分标准进行腕关节功能评价。结果:26例患者均获得随访,时间10~18(13.4±0.8)个月。所有骨折均获得骨性愈合,时间8.5~15.8(11.4±0.5)周。所有患者手术切口都Ⅰ期愈合,无伤口感染、血管神经损伤及内固定失效等病例。术后12个月GarthndWerley评分(3.65±0.36)分,优16例,良8例,可2例。结论:通过掌侧Henry入路,使用蝶形钢板切开复位内固定治疗桡骨远端双柱Die-punch骨折,可获得满意的临床疗效。

Optimal Design of a Main Driving Mechanism for Servo Punch Press Based on Performance Atlases

The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and energy saving.To effectively improve the performance and lower the cost,it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices.A new patented main driving mechanism and a new optimal design method are proposed.In the optimal design,the performance indices,i.e.,the local motion/force transmission indices ITI,OTI,good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined.The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis.Thereafter,the performance atlases,which can present all possible design solutions,are depicted.As a result,the feasible solution of the mechanism with good motion/force transmission performance is obtained.And the solution can be flexibly adjusted by designer according to the practical design requirements.The proposed mechanism is original,and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.

Microstructure evolution of Al-Cu-Mg alloy during rapid cold punching and recrystallization annealing

The microstructure evolution of spray formed and rapidly solidified Al-Cu-Mg alloy with fine grains during rapid cold punching and recrystallization annealing was investigated by transmission electron microscopy(TEM). The results show that the precipitates of fine-grained Al-Cu-Mg alloy during rapid cold punching and recrystallization annealing mainly consist of S phase and a small amount of coarse Al6Mn phase. With the increase of deformation passes, the density of precipitates increases, the size of precipitates decreases significantly, and the deformation and transition bands disappear gradually. In addition, the grains are refined and tend to be uniform. Defects introduced by rapid cold punching contribute to the precipitation and recrystallization, and promote nucleation and growth of S phase and recrystallization. Deformation and transition bands in the coarse grains transform into deformation-induced grain boundary during the deformation and recrystallization, which refine grains, obtain uniform nanocrystalline structure and promote homogeneous distribution of S phase.

Effect of aging treatment on evolution of S'phase in rapid cold punched Al−Cu−Mg alloy

High-resolution transmission electron microscopy(TEM),X-ray diffractometer(XRD),and hardness test were used to study the evolution of long plate-shaped S'phase in the spray-formed fine-grained Al−Cu−Mg alloy during aging after rapid cold punching deformation.Results show that the long plate-shaped S'phase in the extruded Al−Cu−Mg alloy undergoes evident distortion,brittle failure,separation and redissolution,during rapid cold punching deformation,leading to the transformation of long plate-shaped S'phase into short rod or even redissolution and disappearance,causing the matrix to become a supersaturated solid solution.After the aging treatment,the reprecipitation of the phases occurs,and these aging phases are mainly long plate-shaped and granular.The incompletely dissolved S'phase acts as nucleation core,promoting uphill diffusion of the surrounding solute atoms.The S'phase gradually grows with increasing the aging time.The completely dissolved S'phase forms the incoherent equilibrium phase with the matrix to reduce its free energy.After rapid cold punching,the aging response of the deformed Al−Cu−Mg alloy is accelerated,and the hardness of the alloy is substantially increased.

LOCAL CREEP EVALUATION OF P92 STEEL WELDMENT BY SMALL PUNCH CREEP TEST

The aim of this research is to evaluate the local creep damage of various microstructures such as coarse grained heat affected zone （CGHAZ）, fine grained heat affected zone （FG- HAZ）, intercritical heat affected zone （ICHAZ） known as Type IV region, weld metal, and base metal of P92（9Cr-2W） steel weldment by small punch （SP） creep test at 600~ C. Also, to determine the weakest local part of the weldment, the effect of microstructures on creep rupture behavior in the weldment of P92 steel was studied. From the experimental results, the FGHAZ and Type IV region turned out to be very weak local parts of P92 weldment. Especially, the TYPE IV region showed the greatest displacement rate and had the shortest rupture life with many creep cavities widely spreaded in most of the region.

UDP Hole Punching在视频会议系统中的应用

随着宽带网络技术的发展,基于IP网络的多点视频会议系统得到了广泛的应用。为了解决网络地址资源匮乏的问题,大量企业和部门的网络采用内部IP地址,通过NAT路由器与公共网络通信,但是NAT技术在某些情况下又给用户之间的通信造成了一些困难。深入研究了基于UDPHolePunching穿透NAT路由器进行通信的方法,在此基础上设计并实现了一套实用的多媒体多点视频会议系统。

Elastic and plastic deformation behavior analysis in small punch test for mechanical properties evaluation

In order to estimate deformation and mechanical properties of material accurately,elastic and plastic deformation behavior of small punch test was discussed in this paper.A two-dimensional finite element model was established based upon the Gurson-Tvergaard-Needleman(GTN)equation.According to the integration of load–displacement curves with different displacements,the evolution of elastic energy was obtained.The results show that the elastic energy increases quickly in the initial region and tends to be an approximate constant during the plastic bending phase.Meanwhile,an obvious change of the slope of load–displacement curve can be found in the elastic-plastic transition region.The macroscopic deformation and fracture feature were also discussed in order to verify the deformation analysis.Finally,the yield strength,tensile strength and elongation of AISI304 were obtained based on the analysis of deformation energy and percent fracture deflection.The results have a good agreement with that of conventional tensile tests,which may provide a theoretical basis of small punch analysis.

Sheltering effect of punched steel plate sand fences for controlling blown sand hazards along the Golmud-Korla Railway:Field observation and numerical simulation studies

Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.

Microstructure,mechanical,and corrosion properties of surface of CuNi alloy produced by punching and annealing treatment

The influence of annealing on the formation of nanocrystalline of CuNi alloy surface was investigated by evaluating the microstructure, mechanical properties, and corrosion behavior of asprocessed condition （using severe plastic deformation by punching process） and its annealed condition. It was observed that the microstructure changed after annealing of punched sample using an atomic force microscope. Mechanical resistance and corrosion resis tance were also characterized using nanoindentation test, electrochemical test, electron work function, and micro tribometer test. It was found that the punched and sub sequent annealed samples have increasing hardness, elastic behavior 07）, and corrosion resistance. Therefore, anneal ing can lead to the final formation of nanocrystalline and corresponding stability of grain boundary, which are responsible for the increasing mechanical properties and corrosion resistance.

Reduced power consumption in stirred vessel with high solid loading by equipping punched baffles

Solid-liquid suspension in stirred tank is a common operation in the chemical industry. The power consumption, flow pattern and flow field instability of three systems named as unbaffled stirred tank, traditional baffled stirred tank and punched baffled stirred tank(Pun-BST) were studied by using the computational fluid dynamic analysis. Results showed that perforating holes in the baffles could reduce power consumption of mixing. Meanwhile, the punched baffle system could maintain the solids in suspension as traditional baffle system. The results also showed that the baffles could increase the “effective flow” of stirred tank even though the whole velocity of the vessel is lower than un-baffled vessel. In addition, both the solid-liquid suspension and “effective flow” were related to instability of the flow field.Perfect solid-liquid suspension results always along with obvious instability of the flow field. But, the strengthening effect of punched baffle on flow field instability mainly happened in the near-wall area.It's because the collision and aggregation among sub-streams induced by holes intensified the unstable fluid flow. On the whole, the Pun-BST system provided much better mixing characteristics and recommended to apply in the industrial process.

Influence of AZ31 sheet treated by cryogenic on punch shearing

Punch shearing is used to form the part in the material process.Cryogenic treatment(CT)has active effect on local mechanical properties of steel,but it is still uncertain of the influence of CT on the properties of the magnesium alloy during punch shearing.In this work,the influence of AZ31 sheet treated by cryogenic on punch shearing was studied.Microstructures were observed with a ZEISS optical microscope,and mechanical properties,as well as shear properties were tested by tensile testing and punch shearing.The results show that the number of secondary phase increases and a large number of twins appear in the grains after CT.Meanwhile,the ultimate tensile strength(UTS),the ductility,and hardness of AZ31 are improved,while the yield strength(YS)decreases gradually during CT.During punch shearing,the shearing strength decreases,the rollover radius changes insignificantly,and the height of the burr on the edge of the cross section decreases.At the same time,a larger proportion of smooth zone on the cross section has been achieved.

Reduce the noise of punch press with the equivalent damping

To reduce the noise of the punch press during the punching process, the polyurethane elastomer is used as the damping material. The experiments of reducing noise were made by means of adding the polyurethane elastomer at different positions on the 100 kN and 1 000 kN punch presses. The better effect of reducing noise was obtained. After researching and analyzing a large number of test data, the ″equivalent damping hypothesis″ is put forward. The hypothesis makes the experiment of reducing noise simpler and also more economical. It is estimated that there is a vast application in the research area of vibration control and noise reduction.