Effect of Heat-Setting on Structural Parameters and Mechanical Properties of PP Monofilament Hernia Patch

General surgery hernia is a common and frequently- occurring disease in the world. In the tension-free hernia repair surgery, polypropylene （PP） patch has been confirmed as the most popular surgical implants. In this study, domestic medical PP monofilament was selected as raw material whose diameter was 0.15 mm, and the patch was knitted in the warp knitting machine of 12E gauge with one bar. Using the method of orthogonal experiment with three factors and three levels, the best heat-setting process of PP mesh was determined at the temperature of 130 ~C with 10 min under tension-free conditions. The relationship between heat-setting tension and performance of the patch was discussed. Patches with different porosity were prepared, and then structural parameters including density, thickness, porosity, and mechanical properties including tensile breaking strength, bursting strength, tearing strength, flexural rigidity and suture pulling out strength were tested and compared. The experimental results show that： the smaller of the patch＇s density, the higher of the porosity; other properties including density, thickness, bending stiffness, tensile breaking strength, bursting strength, tear strength, and suture pulling out strength reduce in varying degrees. This different degree of reduction is worth summarizing.     

Influence of Heat Setting on Mechanical and Structural Properties of Polypropylene Hernia Mesh

Heat setting has important effects on mechanical and structural properties of polypropylene( PP) mesh. However,there is no systematic study on the effects of heat setting. In this paper,the orthogonal array was designed for heat setting,and the influences of heat setting on structural, mechanical properties and flexural rigidity of PP mesh were studied. The experimental results showed that temperature had larger influence than tension and time on thickness,tensile strength,bursting strength, tear strength and bending stiffness of PP meshes, except the fabric weight. The optimum heat setting parameters were as follows: temperature was120 ℃, time was 10 min,and tension was small. These results will provide guideline for the selection of heat setting parameters.     

轻集料颗粒群特征对混凝土力学性能的影响

运用数字图像处理技术研究轻集料的颗粒群特征,采用多种参数表征轻集料颗粒群的粒度和粒形特征.在此基础上,通过灰色关联分析,研究轻集料颗粒群特征对混凝土力学性能的影响.结果表明,当轻集料颗粒群比表面积在520 m2·m-3以上并且颗粒长宽比低于1.34时,所配制的轻集料混凝土能同时达到较高的抗压强度和抗折强度.这为高性能轻集料混凝土的配制提供了依据.     

轻骨料混凝土配合比设计的试验研究

为研究轻骨料混凝土的抗压性能,以奎屯生产的陶粒为轻粗骨料,采用松散体积法设计了6种轻骨料混凝土的配合比,测定了混凝土拌和物的和易性及混凝土的立方体和轴心的抗压强度,轻骨料混凝土的和易性较相同水灰比的普通混凝土差,立方体抗压强度与轴压强度的比值约为0.72。探讨了水灰比和砂率对轻骨料混凝土的强度及密度的影响程度,水灰比与砂率对轻骨料混凝土抗压强度的影响显著,正交分析其极差≥4;水灰比的影响较砂率大,二者极差比为1.68。     

Processing and Mechanical Characterization of Electro-spun Polycaprolactone Membrane Coated Hernia Mesh

Composite hernia meshes designed in this paper consist of polypropylene( PP) knitted meshes and polycaprolactone( PCL)nanofiber membranes,which are produced by electro-spinning the solution composed of PCL as a solute and the mixture of dimethylformamide( DMF) and dichloromethane( DCM) as a solvent. The morphology and diameter of nanofibers in the membrane are well performed when the 15% PCL solution is electrospun under the condition of 18 k V,15 cm,0. 7 m L/h. The poresize of the membranes is less than 10 μm, where such kinds of arrangement are extremely compact to prevent the cells from growing in. The mechanical properties of the membrane with better arrangement state can reach 68. 8 c N/mm~2. The cytotoxicity test of the composite mesh demonstrates the nontoxicity of the materials.However,the bonding fastness between the membrane and the PP mesh is extremely unsubstantial. The better ways to bond PP mesh with PCL membranes should be discussed in the future.     

剪切速率对黄土力学性质及邓肯 张参数的影响

为探究加载速率对原状黄土强度和变形特性及其邓肯-张模型参数的影响,采用SLB-1型三轴剪切渗透试验仪,开展原状黄土在不同围压和剪切速率下的不固结不排水三轴剪切试验,并通过微观试验验证其宏观力学性质。结果表明：在试验参数设定范围内,剪切速率对原状黄土的力学性能有显著影响,不同剪切速率下原状黄土的偏应力－应变关系基本符合双曲线关系;初始变形模量随围压的增大而增大,随剪切速率的增大呈现先增大后减小的规律,原状黄土的黏聚力c、无因次基数K、应力破坏比Rf和破坏强度与剪切速率之间存在明显的临界剪切速率转折点1.7 mm?min-1,此时各参数均达到最大值,无因次指数n无明显规律可循;当剪切速率小于此临界值时,黏聚力c、无因次基数K、应力破坏比Rf和破坏强度随着剪切速率的增大而增大,当超过剪切速率临界值时又有一定程度的降低,总体上呈现先增大后减小的规律,而内摩擦角随着剪切速率的增大而逐渐增大且增大幅度甚微;试样的偏应力－应变曲线无明显的峰值点,呈应变硬化型;通过拟合曲线,得到了原状黄土试样的抗剪强度指标和破坏强度与不同剪切速率之间的拟合公式,以期更好地研究剪切速率的变化对西宁原状黄土力学性能的影响。     

控轧控冷工艺对高强度结构钢组织及力学性能的影响

探讨了控制轧制及加速冷却过程中工艺参数对高强度结构钢组织及性能的影响;借助光学显微镜、扫描电镜、电子背散射衍射对钢的强韧化机制进行了分析.通过合理选择两阶段控轧+快速冷却参数,获得了满足国标GB/T 16270—1996中Q690,Q620和Q550要求的高强度钢板;得出了终轧温度、终冷温度和冷却速度与力学性能之间关系的回归方程,并分析了这些因素对显微组织及力学性能的影响.结果表明:在终轧温度870~880℃,冷速15~20℃/s的条件下,终冷温度570~600℃,能够达到Q550的要求;终冷温度500~570℃,能够达到Q620的要求;冷速提高至35~40℃/s,终冷温度在550℃左右,能够...     

高温后轻质多孔混凝土力学性能试验

通过高温后轻质加气混凝土的力学性能试验,测得了抗压强度、弹性模量和峰值应变与温度的关系.试验表明:高温后轻质加气混凝土的抗压强度在100℃时略微提高,到300℃时逐渐下降,超过300℃时,强度变化不明显;在100℃以内,弹性模量基本保持不变,超过100℃后,弹性模量不断减小,与温度成线性关系;随着温度的升高,峰值应变逐渐增大,呈直线上升趋势.最后分析了不同温度下的应力-应变曲线,提出了高温后轻质加气混凝土的本构模型.     

Structure and Mechanical Properties of Polypropylene Hernia Meshes with Various Weight

Polypropylene( PP) is a kind of stable material with excellent mechanical properties. Meshes made of PP have lots of obvious advantages. In this paper,5 PP hernia meshes with different warp-knitting structures which can be sorted into one light-weight hernia mesh,two standard-weight hernia meshes and two heavyweight hernia meshes were chosen to have a serious of mechanical test,including weight density,thickness,pore size,porosity,tensile strength,bursting strength,stitch tear strength,tear strength and bending rigidity. The respective relationship between mechanical performance and weight density were analyzed. The results revealed that heavy-weight hernia meshes had the biggest thickness( 0. 834 mm),the smallest pore size( 462 μm) and the smallest porosity( 58. 40%). The mechanical performance demonstrated that the tensile strength increased more than 800 N,the stitch tear strength increased more than 40 N,the bursting strength increased more than750 N and the tear strength increased more than 40 N by enlarging the weight density by 100-150 g/m~2. However, heavy-weight hernia meshes had problems of high bending rigidity,unevenness and anisotropy. Standard-weight hernia meshes with 70-140 g/m~2 not only met the demand of the mechanical properties,but also had good flexibility and structure parameters,which could be considered as an ideal hernia mesh.     

冷却工艺参数对海洋工程用H型钢组织性能的影响

通过对SM490YB实验钢进行热轧和超快速冷却实验,研究了不同工艺参数对实验钢厚度方向不同位置的显微组织的影响,分析了SM490YB实验钢的强韧化机理.实验结果表明:随着终冷温度的降低,实验钢厚度方向相同位置的贝氏体和针状铁素体含量逐渐增加,多边形铁素体和珠光体含量减少;实验钢的强度和低温韧性随着终冷温度的降低而增加,终冷温度为480℃、返热温度为554℃时,力学性能最佳.冷却速率的增加可以提高实验钢的强度,但过快的冷却速率会损害材料的韧性.     

NiGrMoV钢回火处理时沉淀行为及对机械性能的影响

研究了高强低碳 NiCrMoV 钢淬火后回火温度对显微组织和机械性能的影响,着重分析碳化物的析出规律及对强度的影响,并对此钢提出了最佳热处理制度。试验表明,最佳热处理制度为淬火温度 930—940℃,回火温度 500—600℃。碳化物的形态、种类、分布主要取决于回火温度。450℃ 以下回火,主要为杆状M_3C 型碳化物和少量等轴状Cr_7C_3 沉淀;550℃ 以上回火,主要为杆状或球状 M_3C、等轴状 Cr_7C_3 和针状 Mo_2C。550℃ 回火时产生二次硬化。     

轻骨料夹芯复合墙板及连接节点力学性能试验研究

设计轻骨料夹芯复合墙板试件及与钢结构的连接节点。通过采用低周反复加载试验,研究其力学和抗震性能,确定其破坏形式,根据试验数据获得了(p-Δ)滞回曲线和骨架曲线,分析耗能和变形性能等。为夹芯复合墙板在轻型钢结构住宅中的应用提供了试验依据。     

高弹性体复合材料动态力学性能试验研究

为应对爆炸恐怖提出了一种由SPUA与高强纤维复合成高弹性复合材料的加工方法. 对SPUA材料进行了准静态和动态力学实验研究,试验结果表明SPUA材料动态力学性能具有应变率相关特性. 基于Mooney-Rivlin模型建立了高弹性体SPUA材料的本构模型. 进一步实验得到了SPUA材料与芳纶编制布材料制成高弹性复合材料的撕裂特性. 实验结果表明撕裂强度增强了约20%.     

二维编织防汛金属网网结结构与力学性能

针对防汛金属网在装载过程中易出现网结断裂的情况,通过对不同编织工艺参数的试样的拉伸性能测试,分析了金属网结拉伸断裂的机理和破坏模式,为进一步研究防汛金属网的强度失效问题奠定基础。结果表明:网节的编织工艺参数对其抗拉强度影响较大。编织角越大,网节结构紧密,网丝无滑移,但一定程度上减低了网节的抗拉强度;网节编织长度小,可以充分发挥网丝的抗拉性能,但结构稳定性较差。     

水泥-聚苯乙烯轻质材料的制备及抗冲击性

采用半干料压缩成型工艺制备一种水泥-聚苯乙烯轻质材料,通过压缩试验获得其应力-应变曲线,采用高低两种冲击能量测试抗冲击性,利用自制装置测试和计算其对冲击力、冲击能量的吸收比,分析了水泥掺量以及纤维、乳胶粉对冲击力、冲击能量吸收比的影响.结果表明:该水泥-聚苯乙烯材料具有与传统聚苯乙烯混凝土完全不同的破坏形式,不发生脆性破坏,具有较高的韧性,在压缩作用下的应变可达到0.6以上;随着水泥掺量增加,材料对冲击力的吸收比先降低后升高,加入纤维、乳胶粉可提高材料对冲击力的吸收比;材料对冲击能量的吸收比先升高后降低,加入纤维、乳胶粉可提高低水泥掺量下冲击能量的吸收比,但降低了高水泥掺量下的吸收比.具体分析了各种因素的影响规律和作用机理.     

一种反应材料制备及准静态力学特性研究

采用热压烧结法制备Zr/W/PTFE反应材料,利用扫描电镜和材料试验机研究其在常态下的微观组织和准静态压缩力学性能;研究结果表明烧结温度过高或过低都会导致Zr/W/PTFE材料密度和强度降低;静态压缩曲线呈现出明显的弹性变形、非弹性变形和应变软化阶段,并具有应变率效应;试件的压缩破坏有劈裂、剪切和劈裂/剪切3种破坏形态. 该材料呈现出黏弹塑性,采用修正的Sargin模型唯象地建立了材料在低应变率范围内的本构模型,模拟结果与实验曲线符合较好.      

分数导数标准线性固体粘弹性材料力学性能研究

分数导数粘弹性模型以及其本构理论能够比经典粘弹性模型更好地描述出粘弹性材料的力学性能.利用基于分数阶理论建立的粘弹性三参数标准线性固体模型,对粘弹性固体材料的储能柔量、耗能柔量、摩擦角、储能模量及耗能模量等性能参数进行分析,并通过数值算例探讨了粘弹性三参数标准线性固体材料部分力学性能的变化规律.研究表明:角频率和分数导数微分算子的阶数对材料的力学性能的影响较大,低频的粘弹性材料可近似看做弹性材料,而高频率的粘弹性材料在一个周期内会发生耗散现象.当角频率等于零时,材料的无量纲存储模量等于1,即粘弹性材料处于橡胶状态;当角频率逐渐增大时,材料的无量纲存储模量和耗散模量等力学性能随着分数导数的阶数的增大而逐渐增加.     

端面磨削动态热力耦合效应及对表面去除过程影响

针对端面磨削加工接触表面热力学分布特征提出一种基于动态热力耦合效应的理论建模方法.首先,建立多颗磨粒运动轨迹数学模型;其次,基于磨粒运动轨迹与磨粒高度的动态分布特征对加工工件磨削力进行解析求解;根据求得的磨削力,运用有限差分法(FDM)对端面磨削工件表面动态热力耦合过程进行分析;最后,分别采用有限元法(FEM)和端面磨削实验验证理论分析的合理性.结果表明:动态热力耦合的均一化程度会引起加工工件表面轮廓高度的差异性,减小砂轮转速可改善加工工件表面轮廓.     

Effects of Stretching Parameters on Morphological and Mechanical Properties of Polytetrafluoroethylene Filaments

Comprehensive performances of polytetrafluoroethylene(PTFE) flat filaments used as suture materials in medical field can be affected significantly by morphological and mechanical characteristics.Due to low tensile strength and non-uniform morphology,PTFE flat filaments cannot be applied widely as medical sutures.In order to solve flaws above,PTFE flat filaments with constant linear density,550 dtex,are manufactured and dependences of morphology,frictional features and mechanical behaviors on stretching ratio and temperature are also analyzed.The results indicate that PTFE flat filaments with high tensile strength(1 922.0 cN) and excellent apparent performance can be manufactured at optimal stretching ratio and temperature,18.0 and350 ℃,respectively.     

掺入豆石的灌浆料在加固工程中的应用

以豆石含量为变化参数,设计了5种灌浆料的配合比,通过试验方法,研究了灌浆料的施工性能（包括坍落扩展度（SF）、T500流动时间和L型仪试验）和抗压强度。试验结果表明,豆石含量增加,灌浆料T500流动时间变短;而坍落度和扩展度（SF）变大;抗压强度降低。工程实例说明,掺入合适豆石的灌浆料能够满足工程应用的要求。