提高某型发射装置限力机构剪切销合格率研究

介绍了某型发射装置限力机构剪切销的设计原理及生产控制分析,通过多项试验对可能影响剪切力值的要素进行了逐一筛选,找到了影响剪切力值的关键因素,通过改进措施使该产品的报废率降低到最小。     

35CrMo钢的调质工艺控制

支座的限位结构设计中要求剪切销的屈服强度波动幅度小于5%,为了使材料的性能满足设计要求,需要对调质过程中的温度和时间进行严格控制。对比淬火温度、回火温度以及各自的保温时间对材料强度和韧性的影响,结果表明,回火温度及其保温时间是影响材料强度和韧性的主要因素。通过试验验证,将回火温度波动控制在±15℃以内,回火时间在60—120 min以内可使调质后的35CrMo满足设计要求。     

浅析水轮机发生多根剪断销剪断事故时的应急处理

本文重点分析了水轮机运行中发生多根剪断销剪断事故时的风险因素,并提出了发生多根剪断销剪断事故时的应急操作步骤以及检修完毕后的恢复操作步骤,以供参考。     

TC1 电阻微焊接接头显微组织及力学性能

目的 研究不同工艺参数（焊接电流、焊接时间）对金属箔材精密电阻微焊接头机械性能的影响。方法 采用电阻微焊接技术对0.05 mm 厚的TC1 箔材进行点焊连接试验,通过拉伸-剪切试验对焊接接头进行力学性能检测,利用硬度网格法结合金相观察,对焊接不同区域进行有效预测。结果 当焊接电流为400 A时,焊核直径随着焊接时间的增加而明显增大,而采用更高的焊接电流时,焊接时间对焊接直径没有显著影响。焊点接头的剪切力随着电流的增大而增大;在所有参数条件下,过长焊接时间都造成了焊点接头剪切力不同程度的减小。此外,由于微观组织的变化,不同焊接区域显现出不同硬度值,其中焊核硬度>母材硬度>热影响区硬度。结论 焊接电流对TC1 电阻微焊接接头力学性能影响较大;硬度网格法可以有效预测焊接不同区域。     

舵机装置活塞连接销剪断故障分析

对一种舵机装置的活塞连接销的剪断故障进行了综合分析，最终得出导致销子剪断的原因并非材料及工艺等因素，而是试验时不注意操作造成压强过程冲超过了销子的剪断强度所致。     

中厚板圆盘剪剪切力能参数测试及最佳剪刃间隙数学模型的建立

针对中厚板圆盘剪剪切质量差、剪切力理论计算偏差大等问题开展了生产实测、数据采集、回归拟合处理,得出现有的剪切力理论公式计算结果和实测结果相比误差在-9.56%～+56.5%之间.这些理论公式求解中未考虑随着厚度的增加剪切抗力和抗剪面积的非线性变化,导致剪切力计算结果大幅减小.这些公式适宜于薄规格钢板的剪切力计算,但用于厚板剪切力计算还要进一步完善.同时,建立了一个综合剪切钢板厚度、材料属性、累积剪切面积的圆盘剪剪刃间隙调整模型,并且考虑了刀盘装置在剪切受力过程中的变形对剪刃间隙影响.因此,针对不同的圆盘剪设备,要在该模型中考虑刀轴载荷-变形值的影响,对模型进行修正完善,就可获得适合于自己的间隙调整工艺参数.     

大尺寸安全销实物单面剪切试验装置及方法

介绍了轧机等大型关键设备所配备的大尺寸安全销实物单面剪切试验装置与试验方法。实物单面剪切试验与小试样性能试验两种方法的结果对比表明，大尺寸安全销实物单面剪切试验是无法用小试样性能试验替代的。     

斜刃倾角对斜刃剪切效果的影响

推导了斜刃倾角取不同数值时，剪切力的计算公式，分析和探讨了在斜刃剪切时，斜刃倾角的大小对剪切力及冲裁件的加工质量的影响。在实际生产中，对于合理选择斜刃倾角的大小，正确地计算剪切力具有重要的指导意义。     

采空区群动力响应的类层间剪切模型法研究

为研究采空区群内岩体介质动力响应特性,提出采空区群动力响应的类层间剪切模型法。通过将上覆岩层等效为由"虚拟间柱群"和集中质量块组成的系统,将周边围岩等效为剪切力Q的作用,构建采空区群类层间剪切模型,建立采空区群内岩体介质的动力响应微分方程;考虑到单元空区的赋存深度和构成形状特征,引入剪切力影响因子δ,修正围岩的剪切力作用。以某金矿5个中段采空区组成的采空区群为例,利用数值分析法与该分析方法进行对比分析。结果表明:上述采空区群赋存环境的等效方法具有可行性;采空区群岩体在其内部阻尼及外部围岩剪切力的双重作用下,作振幅衰减振动;类层间剪切模型法和数值分析法计算记录点的位移、速度时程曲线趋势一致、幅值相近,但前者运算时间更短、效率更高。类层间剪切模型法为研究采空区群动力响应特性提供了一种新思路。     

弹性圆柱销开裂失效分析

某设备在维护过程中发现设备内的弹性圆柱销开裂失效,通过宏观观察、化学成分分析、硬度测试、金相检验、断口分析、氢质量分数测定等方法对弹性圆柱销的失效原因进行了分析。结果表明:弹性圆柱销在退镀工序后没有进行相应的除氢工序,氢渗入了圆柱销内部,导致该弹性圆柱销发生氢脆失效。     

Facile and size-controllable preparation of graphene oxide nanosheets using high shear method and ultrasonic method

ABSTRACT

The lateral size of the graphene oxide (GO) nanosheets could be controlled by preparation method, and a simple and effective strategy to adjust the lateral size of GO nanosheets by selecting suitable method is presented. The high shear method was introduced to produce GO nanosheets, and the GO nanosheets (few micrometres) prepared by high shear method is about one order of magnitude larger than GO nanosheets (few hundred nanometres) obtained by ultrasonic method, as evidenced by atomic force microscopy. The FTIR, XPS and Raman analysis revealed that there are no distinct differences in composition and functional groups between the GO nanosheets produced by high shear method and ultrasonic method. The cavitation in the procedure of ultrasonic method is favourable for GO exfoliation, but it also could result in damage to GO nanosheets. The shearing force in the process of high shear method is effective for GO delamination with minimal fragmentation. The results indicated that the high shear method proposed in this paper is an efficient exfoliation means to produce single-layer GO nanosheets.     

Friction stir welding of al 6061‐T6 thick plates: Part I ‐ experimental analyses of thermal and mechanical phenomena

Abstract

In friction stir welding (FSW), heat is generated by two mechanisms: (1) the friction between the rotating tool and the workpiece at the interface, and (2) the plastic shear deformation of the material in the vicinity of the pin tool. The amount of heat generated is crucial to the quality of the weld. In addition, the mechanical force and torque developed in the process dictates the life of the tool as well as the design of the fixture. In this paper, a butt joint was made by FSW on two thick plates (thickness = 37.6 mm) of aluminum alloy 6061‐T6. The joining was conducted by load control mode (applying a controlled vertical plunging force). Two different tests were performed, one using a long probe pin (24.3 mm in length) and the other using a very short pin (3.5 mm in length). The objectives of the research were to study the heat generation process from the shoulder, the pin, and the mechanical process parameters.

In this Part I, we report on the welding process parameters, i.e. tool RPM, welding speed, tool plunge‐in depth, force, torque, and power history, and the transient temperature history measured from thermocouples. It was found that (a) a quasi‐steady state existed after the tool moved about 82.2 mm from the starting point, during which the tool forces, torque and generated heat reached an equilibrium state in the neighborhood of the tool, (b) the highest temperature measured in the weld seam was less than the melting temperature of the workpiece material, (c) the tool pin plays an important role in the heat input to the process, and (d) the heat generated from the pin strongly depends on its length. The comprehensive test data could be used by researchers interested in numerical modeling of the FSW process without duplicating the complicated tests.     

Effect of hole lubrication on the fretting fatigue life of double shear lap joints: An experimental and numerical study

In this research the affect that lubrication at a hole and pin connection has on the fatigue life of a double shear lap joint is studied both experimentally and numerically. The study focuses on the joint middle plate item, which is connected via a central hole to the outer plates by means of a clearance fitting pin, thereby placing the hole in double shear. In the experimental work three identical batches of fatigue specimens, which are made from aluminum alloy 2024-T3, were fatigue tested. In the first batch the surface of the fastener hole was not lubricated whilst the hole in the other two batches was lubricated – each batch using a different lubricant. The three batches of double shear lap joint specimens were fatigue tested and their S–N curves established. The results show that the specimens in which the holes were lubricated have better fatigue lives than the non-lubricated hole specimens. In the numerical study, FE simulations were performed to include hole lubrication effect on the stress distribution by using different friction coefficient at the interface of the hole and its fastener (pin). The FE results have helped to gain an understanding of the reasons for fatigue life improvement and also have helped to quantify the level of improvement.     

Role of tool pin profiles on wear characteristics of friction stir processed magnesium alloy ZK60/silicon carbide surface composites

Poor friction and wear resistance are the major drawbacks that restrict structural applications of ZK60 magnesium alloys. The surface properties of magnesium alloy can be enhanced by reinforcing particles in the surface using friction stir processing (FSP). Tool pin profile is the significant process parameters which influences the material flow, particle breakups and its distribution in the processed zone. In this study, an attempt was made in order to understand the major effects of tool pin profiles namely, cylindrical thread (CT), plain cylindrical (PC), plain tapered cylindrical (PTC) and square (SA) pin profiles on the microstructure characteristics and particle distribution of friction stir processed/silicon carbide particle surface composites. The surface composites fabricated by plain tapered cylindrical pin profile yield superior properties which is attributed to the higher shear force and balanced state of material flow and heat generation in the processed zone. The formation of smaller grains and hardness enhancement due to dispersion strengthening are the main causes to get better wear resistance of friction stir processed/silicon carbide particle magnesium alloy.     

块石含量和空间分布对土石混合体抗剪强度影响的离散元分析

土石混合体的抗剪强度在很大程度上取决于其块石的含量、空间分布、形态等参数。该文采用球体单元模拟土颗粒,通过组合颗粒单元构造非规则形态的块石,对不同含石量和块石空间分布下土石混合体的直剪过程进行了离散元数值模拟。计算结果表明,在低含石量下,土石混合体的抗剪强度随含石量的增加而增加;在中含石量下,受块石空间分布的影响,其抗剪强度呈现很强的波动性;在高含石量下,其抗剪强度显著增强,波动性相对较小。抗剪强度在中高含石量下波动现象的细观机理是块石空间分布影响下的力链结构特性。当块石的空间分布使其形成较强力链结构时,抗剪强度较高;反之,块石间的力链结构不稳定,抗剪强度相对较低。以上研究有助于从细观尺度揭示土石混合体变形和剪切强度特性的内在机理。     

剪切增稠胶/碳酸钙复合材料的制备及其抗冲击性能研究

为了提升人体防护装备的轻便性和灵活性,以剪切增稠胶(STG)为基体,并用纳米CaCO₃对其进行补强,制备了缓冲吸能性能优异的剪切增稠STG/CaCO₃复合材料,研究了CaCO₃含量和粒径对STG剪切增稠性能的影响。结果表明:添加CaCO₃后复合材料的最大储能模量比未添加时增加455%;添加的CaCO₃粒径越小,复合材料的剪切增稠性能越优异。通过落锤冲击实验表征了复合材料的抗冲击性能,CaCO₃的填充可使复合材料在具有最小变形量的情况下吸收更多的冲击力。探究了STG剪切增稠和CaCO₃补强的作用机理,指出剪切增稠现象是由交联键的形成和分子链的缠结作用产生的,CaCO₃通过吸能阻裂,分散冲击力产生补强作用。     

钢管混凝土框架-RC剪力墙混合结构滞回性能分析

为了研究带钢管混凝土边柱钢筋混凝土(RC)剪力墙的抗震性能,在其他研究者完成的带钢管混凝土边柱RC剪力墙和普通钢筋混凝土剪力墙滞回性能试验结果的基础上,采用开源非线性分析程序OpenSees平台中的非线性纤维模型对其进行了低周往复试验的数值模拟,通过直接在截面层次定义非线性剪切恢复力的方法来模拟纤维截面的抗剪。计算结果与实测结果总体吻合较好,研究表明：这种考虑剪切效应的纤维模型法能够较好的模拟该类组合剪力墙的抗剪承载力、捏缩效应以及刚度退化,而且运算效率较高。     

TC4钛合金构件电磁铆接极限间隙量研究

维修中拆卸原铆钉将导致钉孔间隙明显增大,进而直接影响维修后铆接构件性能.为了实现大间隙量下钛合金铆接构件的有效维修,本文通过试验对TC4钛合金构件电磁铆接极限间隙量进行了研究,并评估了铆接构件拉剪性能.结果表明:电磁铆接通过绝热剪切成形的方式,能有效实现大间隙量下钛合金构件的干涉铆接;随着钉孔间隙量的增加,镦头直径和高度均呈现出近线性递减,尽管钉杆成形后直径明显增大,但干涉量却减小;拉剪试验中,试件分别发生拉弯和剪切失效,拉脱性能对钉孔间隙量不敏感,但试件剪切屈服强度和失效强度均随着钉孔间隙量的增加而明显提高;对于4 mm钛合金铆钉,建议极限钉孔直径为4.3 mm.