An approach for optimization of the wall thickness (weight) of a thick-walled cylinder under axially non-uniform internal service pressure distribution

Today, improving the weight/load carrying capacity ratio of a part is the matter of studies in most of the scientific and industrial areas.Autofrettage dimensions, the amount of material removed from outer and inner radius while manufacturing and the service pressure applied affect the residual stress distribution throughout the wall thickness and hence the load-bearing capacity of a thick-walled cylinder. Calculation of residual stresses after autofrettage process and optimization of autofrettage outline dimensions by using the amount of service pressures applied are common issues in literature.In this study, mandrel-cylinder tube interference dimensions were renovated by using traditional methods for swage autofrettage process of a gun barrel. Also, the residual stresses in the cylinder after autofrettage process, inside and outside material removal process and the variable service pressure throughout the cylinder applied were taken into consideration and incorporated into the design. By using the constrained optimization method, wall thickness(thus the weight) was optimized(minimized)to achieve the specified safety factor along the length of the cylinder. For the same cylinder, the results of the suggested analytical/with residual stress calculation approach were compared to analytical/without residual stress calculation results and numerical topology optimization method calculation results. Since the experimental measurement results are not yet available, it was not possible to compare them with the calculation results.The suggested approach enabled 22.9% extra weight reduction in proportion to numerical topology optimization and enabled 4.2% extra weight reduction in proportion to analytical/without residual stress optimization.Using this approach, the gain from residual stresses after autofrettage operation, the loss of residual stresses after material removal, and the effects of service pressures can be taken into account for each stage of design.

Effect of Molecular Weight and Molecular Distribution on Skin Structure and Shear Strength Distribution near the Surface of Thin-Wall Injection Molded Polypropylene

In this study, the relationship between skin structure and shear strength distribution of thin-wall injection molded polypropylene (PP) molded at different molecular weight and molecular distribution was investigated. Skin-core structure, cross-sectional morphology, crystallinity, crystal orientation, crystal morphology and molecular orientation were evaluated by using polarized optical microscope, differential scanning calorimeter, X-ray spectroscopic analyzer and laser Raman spectroscopy, respectively, while the shear strength distribution was investigated using a micro cutting method called SAICAS (Surface And Interfacial Cutting Analysis System). The results indicated that the difference of molecular weight and molecular weight distribution showed own skin layer thickness. Especially, high molecular weight sample showed thicker layer of the lamellar orientation and molecular orientation than low molecular weight sample. In addition, wide molecular distribution sample showed large crystal orientation layer.

The Relationship between Bulk Property and Property Distribution in Thin-Wall Injection Molded PP at Different Molecular Weight and Molecular Weight Distribution

Thin-wall injection molded parts have been paid much attention to the lightweight saving from viewpoints of natural resources saving. In the injection molding, skin-core structure can be found in the parts. This skin-core structure affects the property of completed injection molding parts (bulk property) even if in thin-wall injection molding. However, there is a few research about the relationship between bulk property and internal property distribution in the injection molding specimen. In this study, thin-wall injection molded parts of polypropylene (PP) were prepared by 4 different molecular weight and molecular weight distribution to reveal the relationship between bulk property and property distribution. These characteristics were investigated by using tensile test, fracture toughness characterized by Essential Work of Fracture (EWF) method for bulk property and film tensile test by sliced sample for tensile property distribution. The property distribution test results revealed that the highly bulk property sample had thicker highly mechanical property layer on its surface.

Settlement patterns of mountainous half-filled and half-cut widened subgrade with retaining wall

The settlement of widened highway subgrade in mountainous area is not only affected by the interaction between new and existing subgrade, but also seriously restricted by the external retaining wall. Based on the practical engineering of half-filled and half-cut widened mountainous highway subgrade with external balance weight retaining wall(BWRW), a sophisticated finite element numerical model is established. The evolution law of subgrade settlement is revealed during the whole process of new subgrade filling and BWRW inclination after construction. The settlement component of subgrade is clarified considering whether the existing pavement continues to be used. The results show that the additional settlement caused by the BWRW inclination after construction cannot be ignored in the widening and reconstruction of mountainous highway subgrade. In addition, pursuant to the comprehensive design of subgrade and pavement, the component of subgrade settlement should be determined according to whether the existing pavement continues to be used, while considering the influence of BWRW inclination after construction. When the existing pavement continues to be used, the settlement of the existing subgrade is caused by the new subgrade filling and the BWRW inclination after construction. On the contrary, the settlement is only caused by the BWRW inclination after construction.

Analysis of dynamic stress intensity factors of thick-walled cylinder under internal impulsive pressure

Dynamic stress intensity factors are evaluated for thick-walled cylinder with a radial edge crack under internal impulsive pressure. Firstly, the equation for stress intensity factors under static uniform pressure is used as the reference case, and then the weight function for a thick-walled cylinder containing a radial edge crack can be worked out. Secondly, the dynamic stresses in uncracked thick-walled cylinders are solved under internal impulsive pressure by using mode shape function method. The solution consists of a quasi-static solution satisfying inhomogeneous boundary conditions and a dynamic solution satisfying homogeneous boundary condi- tions, and the history and distribution of dynamic stresses in thick-walled cylinders are derived in terms of Fourier-Bessel series. Finally, the dynamic stress intensity factor equations for thick-walled cylinder containing a radial edge crack sub- jected to internal impulsive pressure are given by dynamic weight function method. The finite element method is utilized to verify the results of numerical examples, showing the validity and feasibility of the proposed method.

Effect of molecular weight on the quality of poly(alpha-methylstyrene) mandrel

Hollow poly(alpha-methylstyrene)(PAMS)shows application in inertial confinement fusion experiments as the degradable mandrels of glow plasma polymer shells.However,the molecular weight of PAMS has great influence on the quality of mandrels.In this work,this influence was systematically studied using several PAMS samples with different molecular weights.For PAMS shells with 900 mm inner diameter and different wall thickness,when the molecular weight of PAMS is in the range of 300e500 kg·mol^(-1),perfect sphericity and good wall thickness uniformity can be obtained.In contrast,when increasing molecular weight to 800 kg·mol^(-1),the sphericity and the wall thickness uniformity become worse.Moreover,compared with the wall uniformity,the sphericity of PAMS shells was much less sensitive to the molecular weight.The results also showed that the stability of W1/O compound droplets of PAMS shells were less affected by the molecular weight.It was revealed that the wall uniformity and the sphericity of the PAMS shells were associated with the diffusion rates of fluorobenzene(FB).

木结构墙体空气声隔声性能

【目的】研究全频段范围内木结构墙体空气声隔声性能,明确限制常规构造木骨架墙体隔声性能的瓶颈,揭示设置隔声垫层、改变骨架类型、设置窗体等设计参数对墙体隔声性能的影响规律,提出高空气声隔声等级的木结构墙体体系,为木结构墙体在装配式建筑中的高效应用提供技术支撑。【方法】通过小尺寸材料层面的阻抗管法试验,比较分析60~6300 Hz频率范围内工业级弹性橡胶板(橡胶板)、聚氨酯橡胶隔音减震板(聚氨酯板)和聚苯乙烯挤塑板(XPS板)等隔声垫层的隔声性能;基于实验室法开展全尺寸墙体在100~5000 Hz频率范围内的隔声试验,通过1/3倍频程频段18个中心频率对应的单值隔声量,得到墙体计权隔声量(R_(w))、频谱修正量和隔声等级,并与装配式建筑中广泛应用的蒸压加气混凝土(ALC)墙体和正交胶合木(CLT)墙体进行比较。【结果】相较同一厚度的聚氨酯板和XPS板,全频段范围内橡胶板的隔声量较高,且其隔声性能随板厚增加而提高,试验范围内,10 mm厚橡胶板隔声效率最高。常规构造木骨架墙体的隔声量整体上随声波频率增加而提高,该墙体体系在125和3150 Hz处分别出现明显的共振隔声低谷和吻合隔声低谷,其R_(w)为43 dB,用作隔墙或围护构件时的空气声隔声等级分别为4和3级;在墙骨架和定向刨花板(OSB)间设置10 mm厚橡胶板后,受制于木龙骨的声桥作用,墙体隔声性能提升有限,R_(w)增至45 dB,隔声等级未发生改变,常规构造和设置橡胶板的木骨架墙体体系均不满足现行国家标准对普通住宅墙体的隔声要求。当墙骨架采用轻钢骨架且轻钢骨架两侧均覆面双层石膏板(GB)时,该墙体体系的R_(w)增至50 dB,用作隔墙或围护构件时的空气声隔声等级分别升至6和5级;在石膏板和轻钢骨架间设置10 mm压缩玻璃棉条后,R_(w)增至51 dB,隔声等级未发生改变,该轻钢骨架墙体体系满足现行国家标准对普通住宅墙体的隔声要求。与200 mm厚单层和复合ALC墙体相比,试验范围内轻钢骨架墙体的厚度和面密度分别降低35%和70%,但空气声隔声性能更高;针对道路交通、企业生产经营和日常生活等噪音对应的频率范围(160~630 Hz),该轻钢骨架墙体体系的隔声性能增加明显。在常规构造木骨架墙体基础上开洞安装R_(w)为33 dB的窗体,墙体在全频段范围内的隔声频谱特性曲线未发生明显变化,其R_(w)达44 dB,用作隔墙或围护构件时的空气声隔声等级分别为5和4级;常规构造木骨架墙体一侧的GB由单层增至双层、木骨架和OSB间设置10 mm厚橡胶板、木骨架和GB间设置金属减震龙骨制成复合墙体,在复合墙体上安装窗体,该墙体的R_(w)增至48 dB,且在低频段下的共振隔声低谷和高频段下的吻合效应低谷消除或明显变浅,用作隔墙或围护构件时的空气声隔声等级分别升至6和5级,满足现行国家标准对普通住宅墙体的隔声要求。【结果】与木骨架墙体相比,CLT墙体的空气声隔声性能较低;共振隔声低谷、吻合隔声低谷和声桥效应是限制常规构造木骨架墙体隔声性能的瓶颈因素,导致该墙体体系不能满足现行国家标准对普通住宅墙体的隔声要求。将木骨架替换为轻钢骨架,并设置隔声垫层、增加墙面板数量,能够有效提高墙体的空气声隔声性能。

建筑外墙砖饰面安全风险评估模型

建筑外墙砖脱落事故频发,不仅破坏了建筑外观,更是危及居民人身安全。然而砖饰面损坏因素复杂,目前缺少可量化的风险评估模型。基于影响显著、易获取、可量化原则,选取距离上一次全面维修的年限、裂缝数量和立面空鼓面积比,作为外墙砖饰面安全风险评估的量化指标。通过对74个项目进行统计分析,综合运用信息量权重法和专家打分法,确定距离上一次全面维修的年限、裂缝数量和立面空鼓面积比的权重分别为0.20,0.41,0.39。最后通过项目验证,根据提出的安全风险计算模型,当安全风险分值达到40分时,外墙砖饰面发生高坠的风险概率较大。

通过嵌合管来增强负Poisson比结构的耐撞性能

为了提高结构耐撞性,从而实现车辆轻量化,提出了一种嵌合管(由薄壁方形管嵌入双箭头格子而组成的)具有负Poisson比的增强型结构。通过负Poisson比的收缩效应,来增强负Poisson比结构和嵌合管的耦合作用。建立了增强型结构的有限元模型,并通过压缩试验,来验证其准确性;通过数值方法,在轴向载荷下,比较双箭头点阵结构、结构填充管和嵌合管负Poisson比增强型结构的耐撞性能,并进行了参数分析。结果表明:与双箭头点阵结构和填充管结构相比,增强型结构的总吸收能量为1.12 MJ,提升了约40%;比吸能13.2 kJ/kg,提升了约30%;短梁的夹角70°、长梁的夹角40°、长梁厚度1.4~1.6 mm、短梁厚度1.2 mm的结构填充管结构,具有较大的比吸能和较小的碰撞峰值力;增加嵌管厚度显著提升耐撞性能,但结构质量急剧增加,嵌管厚度达到1.2 mm左右时,兼顾耐撞性和轻量化的需求。

酶法提取灵芝孢子粉胞壁水溶性糖的工艺优化及分子量分布

为提高灵芝(Ganoderma lucidum)孢子粉胞壁水溶性糖的提取效率,以灵芝孢子粉胞壁残渣为研究对象,用单因素实验、响应面实验优化酶法胞壁水溶性糖提取工艺,并比较酶法和不同物理法处理的灵芝孢子粉胞壁水溶性糖的分子量分布。结果表明:最佳提取工艺为溶壁酶加量2%,酶解时间5 h,料液比1︰10(g︰m L)、温度40℃、pH6.5,在此条件下提取的灵芝孢子粉胞壁水溶性糖含量达到17.86%。分子量分布分析结果表明,酶解后的水溶性糖以低聚糖为主。研究结果可为有效利用和开发灵芝孢子粉提供参考。

地震荷载作用下土工格室挡墙力学性能的影响因素

借助FLAC3D软件,建立土工格室柔性挡墙支护边坡数值模型,并采用振动台试验结果对数值模型进行验证,采用标定后的数值模型,系统研究了条带刚度、格室尺寸、挡墙厚度和充填料弹性模量4种因素对边坡动力响应的影响,并对挡墙的破坏机理进行了深入探讨,计算了各参数的影响权重。研究结果表明:地震作用下挡墙的稳定性与4种因素有着密切的联系;格室约束围压和永久水平位移沿高程分布规律基本一致,均表现为“增加-衰减”的两段形态,坡顶沉降自墙面向坡体延伸表现为两头小中间大的“V”型分布,水平峰值加速度沿高程表现为“增加-衰减-增加”的3段形态;随着刚度的增加,格室约束围压增大,而永久水平位移、坡顶沉降和水平峰值加速度均减小;随着格室尺寸的增加,格室约束围压、永久水平位移、坡顶沉降和水平峰值加速度均增加;随着挡墙厚度和充填料弹性模量的增加,格室约束围压、永久水平位移、坡顶沉降和水平峰值加速度均减小;4种影响因素中,格室尺寸影响权重最大,对格室约束围压的影响权重达到0.996,而挡墙厚度影响权重最小;地震作用下土工格室挡墙结构具有良好的抗震性能,挡墙结构对于地震能量具有一定的衰减作用,满足抗震设防要求。该研究结果对于地震作用下土工格室柔性挡墙的抗震设计及工程应用具有一定的指导作用。

Complementary comments on diagnosis,severity and prognosis prediction of acute pancreatitis

The radiological differential diagnosis of acute pancreatitis includes diffuse pancreatic lymphoma,diffuse autoimmune pancreatitis and groove located mass lesions that may mimic groove pancreatitis.Dual energy computed tomography and diffusion weighted magnetic resonance imaging are useful in the early diagnosis of acute pancreatitis,and dual energy computed tomography is also useful in severity assessment and prognosis prediction.Walled off necrosis is an important complication in terms of prognosis,and it is important to know its radiological findings and distinguish it from pseudocyst.

混凝土结构设计中常见的稳定问题

混凝土结构的稳定问题受重视程度不及钢结构,本文对比中国、欧洲、美国和新西兰的混凝土设计规范中关于结构整体稳定、构件稳定的条文,并结合示例和公式推导,给出相关设计建议。对于整体稳定,刚重比数值受侧向合力位置、建筑重力大小及位置的影响,不应简单地以刚重比的数值来评判不同建筑的整体稳定性。对于构件稳定,分析了几个常见而易被忽视的问题。穿层柱及支撑连桥的框架柱宜考虑二阶效应;对于大跨度梁和长悬臂梁可借鉴外国规范,控制梁的高宽比和侧向无支撑长度;通过数值屈曲分析来反算柱子计算长度时,应正确施加荷载;国内对墙肢的稳定限制较严,对比墙肢的稳定等效荷载与轴压比限值荷载,给出了楼梯间外墙和L形剪力墙的截面由稳定控制的临界高度。

装配式轻钢龙骨复合外墙隔声性能实验研究

提升装配式轻钢龙骨复合外墙的隔声性能将有效促进绿色建筑发展并提高建筑品质。文章通过隔声实验室测量了6种不同构造组成的装配式轻钢龙骨复合外墙的隔声性能,对比分析了纤维水泥板与石膏板做覆面板、不同厚度内填吸声材料、构件连接处的减振处理及不同厚度外保温装饰板对隔声性能的影响。结果表明:覆面板采用纤维水泥板比采用石膏板对提高隔声性能更有利;轻钢龙骨空腔填充吸声材料的越厚,墙体隔声性能越好;墙体构件连接处进行减振处理,对隔声性能的改善不明显;附加外保温装饰板及增大外保温装饰板的厚度并不能改善装配式轻钢龙骨复合外墙的隔声性能。文中的研究结果可为装配式轻钢龙骨复合外墙的设计生产提供数据支撑和重要参考。

多模态磁共振技术在脑小血管病中的应用进展

脑小血管病(Cerebral Small Vessel Disease,CSVD)是一种与年龄相关的慢性、进行性小血管疾病,影响小动脉、毛细血管和小静脉,与缺血性卒中和痴呆的高发生率密切相关,并可能导致运动、步态和情绪障碍。磁共振成像(Magnetic Resonance Imaging,MRI)在CSVD的诊断中起关键作用,其典型表现为皮质下小梗死、脑白质高信号、腔隙、脑微出血、血管周围间隙和脑萎缩。由于CSVD的病理机制尚未完全阐明,目前缺乏特异性的治疗方法,因此治疗策略主要集中在管理血管危险因素,以延缓病程进展。随着先进MRI技术的应用,研究已从单纯的影像学特征深入到对CSVD病理学机制的探索。本文综述了多模态磁共振新技术在CSVD中的应用,以提高老年患者的生活质量,减轻社会和家庭负担。

低温下内墙腻子和轻质抹灰石膏的相容性研究

本文探索了环境温度、轻质抹灰石膏和内墙腻子的养护时间、内墙腻子种类、界面剂种类等对内墙腻子和轻质抹灰石膏之间相容性的影响。结果表明:在低温条件下,灰钙基腻子和一般型水泥基腻子与抹灰石膏的粘结强度分别是一般型内墙腻子的6.5倍和9倍,而使用VAE乳液类界面剂涂刷抹灰石膏层,一般型内墙腻子的粘结力增加6.5倍。

哑铃负重上肢摆臂锻炼在促进血液透析病人动静脉内瘘成熟中的应用效果

目的:探讨哑铃负重上肢摆臂锻炼在促进血液透析病人动静脉内瘘成熟中的应用效果。方法:选取2022年1月—2023年6月赣州市立医院收治的80例行动静脉内瘘术血液透析病人作为研究对象,根据随机数字表法分为对照组与观察组各40例,对照组采用常规干预,观察组在对照组基础上实施哑铃负重上肢摆臂锻炼。比较两组病人血管壁厚度、静脉血管内径、动静脉内瘘成熟情况、血液透析中泵控血流量、内瘘成熟时间、Fugl-Meyer上肢运动功能评分量表(FMA-UE)评分、上肢功能指数(UEFT)评分、生活质量评分,统计并比较两组并发症总发生率。结果:干预8周后两组病人静脉血管内径与血管壁厚度较干预前增大且观察组大于对照组(P<0.05);干预8周后观察组病人动静脉内瘘成熟比例及血液透析中泵控血流量高于对照组(P<0.05),观察组病人内瘘成熟时间短于对照组(P<0.05);干预8周后两组病人UEFT以及FMA-UE两项上肢功能评分明显高于干预前,且观察组高于对照组(P<0.05);干预8周后两组病人精神支柱、社会管理、身体状况、情感及家庭情况评分明显高于干预前,且观察组高于对照组(P<0.05);干预8周后观察组病人感染、血栓、手臂功能受损、静脉狭窄和闭塞并发症总发生率(5.00%)明显低于对照组(22.50%),比较差异有统计学意义(P<0.05)。结论:哑铃负重上肢摆臂锻炼可以更好地促进血液透析病人动静脉内瘘成熟,提高病人上肢功能评分,改善病人生活质量,减少并发症发生。

轻质填充墙异型柱边框架抗震性能试验研究

本文重点研究了轻质填充墙异型柱边框架的层刚度衰减过程、承载力和弹塑性性能。

装配式轻质墙体设计方法研究

随着装配式建筑的推广,装配式轻质墙体将大量使用。在梳理各类装配式轻质墙体物理力学性能的基础上,基于条板通用技术条件中的抗弯破坏荷载限值要求,提出了装配式轻质墙体在面外荷载作用下的设计计算方法及连接节点设计方法;基于22片5种轻质墙板在不同高度、不同连接方式以及不同拼缝填料强度条件下的低周反复荷载试验结果,提出了装配式轻质墙体的连接构造措施。以上装配式轻质墙体的计算方法和连接构造要求,均已反映在即将发行的地方标准《四川省装配式轻质墙体技术标准》中,标准的发行必将进一步促进装配式轻质墙体的推广应用。

轻质填充墙异型柱框架弹性阶段地震作用计算

本文在四个模型试验研究基础上，建立了轻质填充墙与异型柱框架共同工作的弹性动力计算模型，给出了结构弹性阶段地震作用的计算方法。