Photoelastic stress freezing analysis of total shoulder replacement systems

Photoelastic stress freezing analyses in the orthopaedic literature have, in the past, been limited to studies where bone-on-bone, bone-on-metal or ultra-high molecular weight polyethylene (UHMWPE)-on-metal constructs are modeled. In these cases photoelastic plastics are used to simulate either bone or UHMWPE as it interacts with a metal implant. In joints such as the shoulder, a UHMWPE component is often cemented directly into the scapula's glenoid concavity using polymethylmethacrylate (PMMA). While a photoelastic material can be used to simulate bone with proper load scaling, UHMWPE and PMMA have very different mechanical properties at elevated stress freezing temperatures as compared within vivo body temperature. In this study, materials were identified such that proper scaling of elastic properties at elevated temperatures was utilized to simulate the metal-UHMWPE-PMMA-bone construct. Stresses on orthogonal planes throughout the glenoid were compared for two different UHMWPE component anchoring geometries (keeled and pegged). High stresses were found at the neck of the glenoid and also at the component-bone interface beneath simulated PMMA inclusions.     

Stress evaluation of Through-Silicon Vias using micro-infrared photoelasticity and finite element analysis

The Through-SiliconVias (TSV) is a key component of three dimensional electronic packaging. Obtaining its stresses is very important for evaluating its reliability. A micro-infrared photoelasticity system with a thermal loading function was built and applied to characterize the stresses of the TSV structure. Through testing it was found that the stress of each TSV is different even if their fabrication technology is exactly the same, that different TSVs obtain their stress free states at different elevated temperatures, and that their stress free states are maintained even when the temperature is further elevated. A finite element model was used to quantitatively determine the stresses of a TSV under different stress-free temperatures. Different virtual photoelasticity fringe patterns were then created based on the principle of photoelasticity and the simulated stresses. Comparing the virtual fringe patterns with the experimental pattern, an appropriate virtual photoelasticity fringe pattern and the corresponding stresses of TSV were determined     

在镉盐胁迫下扇贝鳃组织应激蛋白的研究

采用透射电子显微镜观察了虾夷盘扇贝(Patinopecten yessoensis)鳃组织细胞的超微结构, 发现镉盐能胁迫鳃组织中的腮丝、细胞核和线粒体产生病变. 利用双向凝胶电泳(2D-PAGE)优化分离扇贝鳃组织的全蛋白, 获得约800个蛋白质斑点, 并筛选出37个由于镉盐胁迫而产生的差异蛋白质斑点. 选用基质辅助激光解吸离子化-飞行时间质谱(MALDI-TOF MS)技术和数据库检索鉴定差异蛋白, 结果发现7个与镉毒性密切相关的蛋白质, 即热休克蛋白70和β-淀粉酶等上调蛋白质及原肌球蛋白、肌动蛋白和钙活化核苷酸酶1等下调蛋白质. 此外, 还发现转录调节子Crp/Fnr家族为低表达蛋白质, 而ABC转运子为高表达蛋白质. 在这些差异蛋白中, 部分蛋白质适合作为连续监测流动海水中镉污染程度及评价其危害性的蛋白指示物.     

On the predictive capabilities of the shear modified Gurson and the modified Mohr-Coulomb fracture models over a wide range of stress triaxialities and Lode angles

The predictive capabilities of the shear-modified Gurson model [Nielsen and Tvergaard, Eng. Fract. Mech. 77, 2010] and the Modified Mohr-Coulomb (MMC) fracture model [Bai and Wierzbicki, Int. J. Fract. 161, 2010] are evaluated. Both phenomenological fracture models are physics-inspired and take the effect of the first and third stress tensor invariants into account in predicting the onset of ductile fracture. The MMC model is based on the assumption that the initiation of fracture is determined by a critical stress state, while the shear-modified Gurson model assumes void growth as the governing mechanism. Fracture experiments on TRIP-assisted steel sheets covering a wide range of stress states (from shear to equibiaxial tension) are used to calibrate and validate these models. The model accuracy is quantified based on the predictions of the displacement to fracture for experiments which have not been used for calibration. It is found that the MMC model predictions agree well with all experiments (less than 4% error), while less accurate predictions are observed for the shear-modified Gurson model. A comparison of plots of the strain to fracture as a function of the stress triaxiality and the normalized third invariant reveals significant differences between the two models except within the vicinity of stress states that have been used for calibration.     

Singularities in a Solution to a Rotating Orthotropic Disk with Temperature Gradient

A semi-analytical solution is obtained for a rotating stress-free edge disk of constant thickness and density. In the plastic range, the Hill’s quadratic orthotropic yield criterion is adopted. In the elastic range, the Hooke’s law holds with thermal effects included. The analysis of singularities performed may be used for correct implementation of numerical codes and preliminary engineering design.     

PDMS梯度光栅结构制备技术研究

由于传统方法制作的梯度光栅,工艺条件苛刻,制作过程复杂,难以控制,制作成本高,周期较长,提出了一种成本低、工艺简单、可大量制备梯度光栅的工艺方法,采用基于刚性薄膜/柔性衬底的自组装工艺和氧等离子体(Plasma)的方法制备了微米尺度的梯度光栅,利用Plasma时间的可控性和聚二甲基硅氧烷(PDMS)优异的弹性制得所需要尺寸的光栅。首先在聚乙烯对苯二酸脂(PET)薄膜上旋涂一层PDMS薄膜,待PDMS薄膜固化后将双层薄膜弯曲并用Plasma处理,在其表面生成一层刚性氧化层,借助柔性的PET对刚性层施加均匀应力,当应力超过临界值时,在PDMS基底上自组装形成光栅褶皱结构。由于弯曲时预应力的变化,所以在PDMS薄膜上会形成周期和高度呈阶梯状的的光栅褶皱,也就是梯度光栅。采用可见光作为梯度光栅的性能测试光源,选用一级衍射光作为检测对象,从图谱中可以看出以PDMS为基底制备的光栅具有很好的衍射效应,并可实现很好的分光效果。实验表明：梯度光栅具有明显的衍射现象,并且衍射角变化显著,可广泛用于应力测量。这种方法制备的柔性梯度光栅也可以作为微型应变装置来检测应力的变化,未来有望用于微型光谱仪、扫描仪、光通讯等领域中。     

The influence of pulse duration on the stress levels in ablation of ceramics: A finite element study

We present a finite element model to investigate the dynamic thermal and mechanical response of ceramic materials to pulsed infrared radiation. The model was applied to the specific problem of determining the influence of the pulse duration on the stress levels reached in human dental enamel irradiated by a CO₂ laser at 10.6 μm with pulse durations between 0.1 and 100 μs and sub-ablative fluence. Our results indicate that short pulses with durations much larger than the characteristic acoustic relaxation time of the material can still cause high stress transients at the irradiated site, and indicate that pulse durations of the order of 10 μs may be more adequate both for enamel surface modification and for ablation than pulse durations up to 1 μs. The model presented here can easily be modified to investigate the dynamic response of ceramic materials to mid-infrared radiation and help determine optimal pulse durations for specific procedures.     

半导体衬底片的应力损伤及其行为

本文根据实际测量结果,一叙述了半导体衬底制片质量对外延生长的影响。特别是,讨论了在 GaAs、InP 衬底中,产生于切片、研磨和抛光加工过程中的机械损伤的影响。     

热蒸发YbF3薄膜的机械特性

 实验研究了热蒸发YbF₃薄膜在大气中的应力和附着力。利用Veeco干涉仪,测试了各种工艺条件下单层YbF₃薄膜的应力。结果发现:YbF₃薄膜的残余应力为张应力,热应力在残余应力中的比重较大;沉积方式对薄膜应力的影响不大;薄膜应力在大气中有一个释放的过程。热处理后,YbF₃薄膜应力增大。