Effect of Thermal Fatigue Loading on Tensile Behavior of H13 Die Steel with Biomimetic Surface

<正> Biomimetic surface is an effective ways to promote the performance grade and applied range of materials without alteringtheir substrate.Many improved properties such as resisting fatigue,enduring wear,etc,have been achieved by applyingbiomimetic morphology or structure to some engineering material surfaces.In this paper,aiming to reveal the relationshipbetween thermal cracking behavior and mechanical properties of engineering materials with biomimetic surface,biomimeticspecimens were fabricated using laser technique by imitating the heterogeneous structure on the surface of plant leaves.Theeffect of thermal fatigue cycling on the tensile properties of H13 die steel specimens with different surfaces (several types ofbiomimetic surfaces and a smooth surface) was compared and investigated.As a result,due to the coupling effects of themorphological features on the surface and the microstructure characteristics within unit zone,these specimens with biomimeticsurface exhibit remarkably enhanced Ultimate Tensile Strength (UTS) and 0.2% Yield Strength (YS) compared with referencespecimens while corresponding ductility remains largely unaffected even heightened,whether the thermal fatigue loads or not.The relative mechanisms leading to these improvements have been discussed.     

Biomimetic Drag Reduction Study on Herringbone Riblets of Bird Feather

Birds have gradually formed various excellent structures such as streamlined shape and hollow shaft of feather to improve their flying performance by millions of years of natural selection. As typical property of bird feather, herringbone riblets align along the shaft of each feather, which is caused by perfect link of barbs, especially for the primary and secondary feathers of wings. Such herringbone riblets of feather are assumed to have great impact on drag reduction. In this paper, microstructures of secondary feathers of adult pigeons are investigated by SEM, and their structural parameters are statistically obtained. Based on quantitative analysis of feather structure, novel biomimetic herringbone riblets with narrow smooth edge are proposed to reduce surface drag. In comparison with traditional microgroove riblets and other drag reduction structures, the drag reduction rate of the proposed biomimetic herringbone riblets is experimentally clarified up to 16%, much higher than others. Moreover, the drag reduction mechanism of herringbone riblets are also confirmed and exploited by CFD.     

Static and Dynamic Mechanics Analysis on Artificial Hip Joints with Different Interface Designs by the Finite Element Method

Four different structural models of artificial joints were developed and the finite element method （FEM） was employed to investigate their mechanical characteristics under static and dynamic conditions. The materials used in the FEM calculation were ultra-high molecular weight polyethylene （UHMWPE）, 316L stainless steel, CoCrMo alloy and Ti6A14V alloy. The stress distribution, strain, and elastic deformation under static and dynamic conditions were obtained. Analysis and comparison of the ~alculation results of different models were conducted. It is shown that with the same parameters the model of a metallic femur head covered with an artificial cartilage layer is more similar to the structure of the natural human joint and its mechanical characteristics are the best of the four models.     

Effect of an Artificial Caudal Fin on the Performance of a Biomimetic Fish Robot Propelled by Piezoelectric Actuators

This paper addresses the design of a biomimetic fish robot actuated by piezoeeramic actuators and the effect of artificial caudal fins on the fish robot＇s performance. The limited bending displacement produced by a lightweight piezocomposite actuator was amplified and transformed into a large tail beat motion by means of a linkage system. Caudal fins that mimic the shape of a mackerel fin were fabricated for the purpose of examining the effect of caudal fm characteristics on thrust production at an operating frequency range. The thickness distribution of a real mackerel＇s fin was measured and used to design artificial caudal fins. The thrust performance of the biomimetic fish robot propelled by fins of various thicknesses was examined in terms of the Strouhal number, the Froude number, the Reynolds number, and the power consumption. For the same fm area and aspect ratio, an artificial caudal fin with a distributed thickness shows the best forward speed and the least power consumption.     

Analysis of the effect of design parameters and their interactions on the strength of dental restorations with endodontic posts,using finite element models and statistical analysis

Many previous studies, both in vitro and with model simulations, have been conducted in an attempt to reach a full understanding of how the different design parameters of an endodontically restored tooth affect its mechanical strength. However, differences in the experimental set-up or modelling conditions and the limited number of parameters studied in each case prevent us from obtaining clear conclusions about the real significance of each parameter. In this work, a new approach is proposed for this purpose based on the combination of a validated three-dimensional parametric biomechanical model of the restored tooth and statistical analysis using full factorial analysis of variance. A two-step approach with two virtual tests (with, respectively, 128 and 81 finite element models) was used in the present work to study the effect of several design parameters on the strength of a restored incisor, using full factorial designs. Within the limitations of this study, and for cases where the parameters are within the ranges that were tested, the conclusions indicate that the material of the post is the most significant factor as far as its strength is concerned, the use of a low Young's modulus being preferable for this component. Once the post material has been chosen, the geometry of the post is of less importance than the Young's modulus selected for the core or, especially, for the crown.     

响应面方法优化菊粉酶液体发酵培养基的研究

目的：为提高菊粉酶的产量。方法：运用Plackett-Burman设计法和响应面分析法,对Kluyveromyces S120液体发酵生产菊粉酶的培养基进行了优化。首先通过Plackett-Burman方法对8个相关影响因素的效应进行评价,并筛选出了有显著正效应的菊芋粉、玉米浆、(NH_4)H_2PO_4等三个因素,其他五个因素没有显著影响。然后根据Box-Behnken的中心组合设计实验和响应面分析方法确定了上述三个主要影响因素的最佳浓度。结果：在优化培养基下,菊粉酶产量为102．82u/mL,是优化前的2．1倍。     

The Effects of Bacterial Surface Adsorption and Exudates on HgO Precipitation

The effects of nonmetabolic bacterial cell wall adsorption and the presence of bacterial exudates on the precipitation of mineral phases from solution is not well constrained experimentally. In this study, we measured the extent of Hg(II) removal from solution, in the presence and absence of nonmetabolizing cells of Bacillus subtilis in both Cl-free and Cl-bearing systems with Hg concentrations ranging from undersaturation to supersaturation with respect to montroydite [HgO_(s)]. Total Hg molalities ranged from 10^?5.00 to 10^?2.00 M at pH 4.50 and 7.00; the ionic strength of the experiments was kept constant using 0.01 M NaClO₄, and the wet mass of bacteria was held constant at 5 g/L for each biotic experiment.

The biotic systems exhibited enhanced Hg(II) removal from solution relative to the abiotic controls in undersaturated conditions. However, thermodynamic modeling of the experimental systems strongly suggests that all of this Hg removal can be ascribed to Hg adsorption onto cell envelope functional groups. There was no evidence for enhanced Hg removal due to precipitation in bulk solutions that were undersaturated with respect to the solid phase. Under the highest total Hg concentrations studied in both the Cl-free and Cl-bearing systems, bacteria inhibit precipitation, maintaining high concentrations of Hg in solution. Cell-free, exudate-bearing control experiments suggest that aqueous complexation between Hg and the bacterially-produced exudates accounts for at least some of the precipitation inhibition. However, a comparison of total available binding sites on the exudates with the concentration of Hg in solution suggests that aqueous complexation alone can not account for the observed elevated final aqueous Hg concentrations in solution, and that the exudates likely exert a kinetic inhibition on the precipitation reaction as well.     

Numerical studies of the influence of various geometrical features of a multispiked connecting scaffold prototype on mechanical stresses in peri-implant bone

Abstract

The multispiked connecting scaffold (MSC-scaffold) prototype is an essential innovation in the fixation of components of resurfacing arthroplasty (RA) endoprostheses, providing their entirely non-cemented and bone-tissue-preserving fixation in peri-articular bone. An FE study is proposed to evaluate the influence of geometrical features of the MSC-scaffold on the transfer of mechanical load in peri-implant bone. For this study, an FE model of Ti-Alloy MSC-scaffold prototype embedded in a bilinear elastic, transversely isotropic bone material was built. For the compressive load on the MSC-scaffold, maps of Huber-Mises-Hencky (HMH) stress in peri-implant bone were determined. The influence of the distance between the bases of neighbouring spikes, the apex angle of spikes, and the height of the spherical cup of spikes of the MSC-scaffold were analysed. It was found that the changes in the distance between the bases of neighbouring spikes from 0.2 to 0.5?mm cause the HMH stress to increase in bone material by 32%. The changes of the apex angle of spikes from 2° to 4° decrease the HMH stress in bone material by 39%. The changes of height of the spherical cup of spikes from 0 to 0.12?mm increase the HMH stress in bone material by 24%. In conclusion, the spikes’ apex angle and the distance between the bases of spikes of the MSC-scaffold are the key geometrical features determining the appropriate MSC-scaffold prototype design. The built FE model was found to be useful in bioengineering design of the novel fixation system for RA endoprostheses by means of the MSC-scaffold.     

应用响应面法优化嗜热脂肪土芽孢杆菌培养基

目的：筛选并优化嗜热脂肪芽孢杆菌CHB1液体发酵培养基。方法：通过Plackett-Burman试验和响应面分析方法,确定培养基的主要影响因素和最佳浓度。结果：利用SAS软件进行分析,确定对响应值影响最大的3个因素为豆粕、酵母粉、K2HPO4。最佳培养基组成为0.51%、豆粕浓度为0.425%、K2HPO4浓度为0.994%。根据模型预测得到的理论最大菌数为2.94&#215;10^8cfu。在初始条件下实验,菌数为2.40&#215;10^8cfu,在优化的最佳培养基条件下,实际的菌数为3.06&#215;10^8cfu。菌数比优化前提高了27.3%。试验值与预测值的误差为4.08%。结论：实验值与模型预测值拟合良好。     

不同耕作方式对陇中旱农区春小麦和豌豆根系空间分布及产量的影响

依托陇中旱农区长期的保护性耕作定位试验,对不同耕作方式下春小麦和豌豆根系空间分布特征及作物产量进行研究,以探索耕作措施影响作物产量的机制.结果表明: 随着生育期的推进,春小麦和豌豆的总根长、根表面积呈先增后减的趋势,开花期达到最大;春小麦根系苗期以0～10 cm最多,花期、成熟期10～30 cm最多;而豌豆根系苗期和成熟期均以0～10 cm最多,花期10～30 cm最多.免耕秸秆覆盖和免耕覆膜增加了根长和根表面积,春小麦和豌豆各生育时期的根长较传统耕作增加了35.9%～92.6%,根表面积增加了43.2%～162.4%.免耕秸秆覆盖和免耕覆膜优化了春小麦和豌豆根系分布,与传统耕作相比,增加了春小麦和豌豆苗期0～10 cm土层根长和根表面积分布比例,花期和成熟期深层次根系分布也显著增加,免耕秸秆覆盖在开花期30～80 cm土层根长和根表面积的分布比例分别比传统耕作提高了3.3%和9.7%.春小麦各生育期的总根长、根表面积与产量呈显著正相关,豌豆各生育期的总根长与豌豆产量呈极显著正相关.免耕秸秆覆盖和免耕覆膜较传统耕作春小麦和豌豆产量增加23.4%～38.7%,水分利用效率提高了13.7%～28.5%.在陇中旱农区,免耕秸秆覆盖和免耕覆膜可以增加作物根长和根表面积,优化了根系在土壤中的空间分布,增强作物根层吸收能力,从而提高作物产量和水分高效利用.     

Effects of several temporomandibular disorders on the stress distributions of temporomandibular joint: a finite element analysis

The aim of this study was to evaluate stress distributions in the temporomandibular joints (TMJs) with temporomandibular disorders (TMDs) for comparison with healthy TMJs. A model of mandible and normal TMJs was developed according to CT images. The interfaces between the discs and the articular cartilages were treated as contact elements. Nonlinear cable elements were used to simulate disc attachments. Based on this model, seven models of various TMDs were established. The maximum stresses of the discs with anterior, posterior, medial and lateral disc displacement (ADD, PDD, MDD and LDD) were 12.09, 9.33, 10.71 and 6.07 times magnitude of the identically normal disc, respectively. The maximum stresses of the posterior articular eminences in ADD, PDD, MDD, LDD, relaxation of posterior attachments and disc perforation models were 21, 59, 46, 21, 13 and 15 times greater than the normal model, respectively. TMDs could cause increased stresses in the discs and posterior articular eminences.     

The effect of implant design of linked total elbow arthroplasty on stability and stress: a finite element analysis

Several linked total elbow arthroplasty designs exist, which function similar to a loose hinge joint. Constraint behaviour is an important design consideration, as it affects joint stability, or how much secondary [e.g. varus–valgus (VV)] motion is permitted. Implant durability is also a concern, as bearing failures have been reported. This finite element analysis investigates the constraint characteristics and ultra high molecular weight polyethylene bearing stresses of three linked elbow design concepts [cylindrical (CY), hourglass (HG) and concave cylinder (CC)]. The bearing of the CY design was subjected to elevated Von Mises stresses (2.1–5.4 times higher than the HG and CC designs) due to edge loading. The HG design maintained low stresses, but was unable to provide consistent VV stability. The CC design also maintained low stresses while providing consistent VV stability. These results suggest that CC designs may provide better stability characteristics and durability in vivo, compared to the other two designs.     

Experimental platform to facilitate novel back brace development for the improvement of spine stability

Abstract

The spine or ‘back’ has many functions including supporting our body frame whilst facilitating movement, protecting the spinal cord and nerves and acting as a shock absorber. In certain instances, individuals may develop conditions that not only cause back pain but also may require additional support for the spine. Common movements such as twisting, standing and bending motions could exacerbate these conditions and intensify this pain. Back braces can be used in certain instances to constrain such motion as part of an individual’s therapy and have existed as both medical and retail products for a number of decades. Arguably, back brace designs have lacked the innovation expected in this time. Existing designs are often found to be heavy, overly rigid, indiscrete and largely uncomfortable. In order to facilitate the development of new designs of back braces capable of being optimised to constrain particular motions for specific therapies, a numerical and experimental design strategy has been devised, tested and proven for the first time. The strategy makes use of an experimental test rig in conjunction with finite element analysis simulations to investigate and quantify the effects of back braces on flexion, extension, lateral bending and torsional motions as experienced by the human trunk. This paper describes this strategy and demonstrates its effectiveness through the proposal and comparison of two novel back brace designs.     

Effects of Methanol on Wettability of the Non-Smooth Surface on Butterfly Wing

The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electron microscopy, The influence of the scale micro- and ultra-structure on the wettability was investigated. Results show that the contact angle of distilled water on the wing surfaces varies from 134.0° to 159.2°. High hydrophobicity is found in six species with contact angles greater than 150°. The wing surfaces of some species are not only hydrophobic but also resist the wetting by methanol solution with 55% concentration. Only two species in Parnassius can not resist the wetting because the micro-structure （spindle-like shape） and ultra-structure （pinnule-like shape） of the wing scales are remarkably different from that of other species. The concentration of methanol solution for the occurrence of spreading/wetting on the wing surfaces of different species varies from 70% to 95%. After wetting by methanol solution for 10 min, the distilled water contact angle on the wing surface increases by 0.8°-2.1°, showing the promotion of capacity against wetting by distilled water.     

The influence of uncemented femoral stem length and design on its primary stability: a finite element analysis

One of the crucial factors for short- and long-term clinical success of total hip arthroplasty cementless implants is primary stability. Indeed, motion at the bone–implant interface above 40 μm leads to partial bone ingrowth, while motion exceeding 150 μm completely inhibits bone ingrowth. The aim of this study was to investigate the effect of two cementless femoral stem designs with different lengths on the primary stability. A finite element model of a composite Sawbones^® fourth generation, implanted with five lengths of the straight prosthesis design and four lengths of the curved prosthesis design, was loaded with hip joint and abductor forces representing two physiological activities: fast walking and stair climbing. We found that reducing the straight stem length from 146 to 54 mm increased the average micromotion from 17 to 52 μm during fast walking, while the peak value increased from 42 to 104 μm. With the curved stem, reducing length from 105 to 54 mm increased the average micromotion from 10 to 29 μm, while the peak value increased from 37 to 101 μm. Similar findings are obtained for stair climbing for both stems. Although the present study showed that femoral stem length as well as stem design directly influences its primary stability, for the two femoral stems tested, length could be reduced substantially without compromising the primary stability. With the aim of minimising surgical invasiveness, newer femoral stem design and currently well performing stems might be used with a reduced length without compromising primary stability and hence, long-term survivorship.     

Computational and Experimental Study of Performance of an Artificial Ligament: DacronTM yarn

Abstract

The success rate of reconstructing the Anterior Cruciate Ligament (ACL) with prosthetic ligaments is currently low both in humans and animals. The stress distribution in prosthetic ligaments that causes failure is very complex and not yet understood. Therefore, we have begun to develop a Finite Element Model of a prosthetic ACL. Here we describe the normal and contact stresses in Dacron^TM yarn (a multi-fibrillar structure) using input data based on experimental measurements of the load and strain of six designed yarns.

The results show that the normal and contact stresses in the fibres of the ACL yarn are directly proportional to the yam strains. Increasing the twisting length (transverse deformation) of the yarn increases the normal stress in the fibres and the yarn modulus, but decreases the contact stresses between the fibres. The structural properties of a yarn are dependent on the specific arrangement of various filament types. Increasing the distance between the longitudinal (symmetry) axes of the filaments and the axis of symmetry of the yarn decreases the stresses.     

Design considerations for ceramic resurfaced femoral head: effect of interface characteristics on failure mechanisms

Ceramic hip resurfacing may offer improved wear resistance compared to metallic components. The study is aimed at investigating the effects of stiffer ceramic components on the stress/strain-related failure mechanisms in the resurfaced femur, using three-dimensional finite element models of intact and resurfaced femurs with varying stem–bone interface conditions. Tensile stresses in the cement varied between 1 and 5 MPa. Postoperatively, 20–85% strain shielding was observed inside the resurfaced head. The variability in stem–bone interface condition strongly influenced the stresses and strains generated within the resurfaced femoral head. For full stem–bone contact, high tensile (151–158 MPa) stresses were generated at the cup–stem junction, indicating risk of fracture. Moreover, there was risk of femoral neck fracture due to elevated bone strains (0.60–0.80% strain) in the proximal femoral neck region. Stresses in the ceramic component are reduced if a frictionless gap condition exists at the stem–bone interface. High stresses, coupled with increased strain shielding in the ceramic resurfaced femur, appear to be major concerns regarding its use as an alternative material.