科创中国

Lightweight design requires an accurate life prediction for structures and components under service loading histories. However, predicted life with the existing methods seems too conservative in some cases, leading to a heavy structure. Because these methods are established on the basis that load cycles would only cause fatigue damage, ignore the strengthening effect of loads. Based on Palmgren-Miner Rule(PMR), this paper introduces a new method for fatigue life prediction under service loadings by taking into account the strengthening effect of loads below the fatigue limit. In this method, the service loadings are classified into three categories: damaging load, strengthening load and none-effect load, and the process for fatigue life prediction is divided into two stages: stage I and stage II, according to the best strengthening number of cycles. During stage I, fatigue damage is calculated considering both the strengthening and damaging effect of load cycles. While during stage II, only the damaging effect is considered. To validate this method, fatigue lives of automobile half shaft and torsion beam rear axle are calculated based on the new method and traditional methods, such as PMR and Modified Miner Rule(MMR), and fatigue tests of the two components are conducted under service loading histories. The tests results show that the percentage errors of the predicted life with the new method to mean life of tests for the two components are –3.78% and –1.76% separately, much lesser than that with PMR and MMR. By considering the strengthening effect of loads below the fatigue limit, the new method can significantly improve the accuracy for fatigue life prediction. Thus lightweight design can be fully realized in the design stage.

Pneumatic actuators and electric actuators have almost been applied to all manufacturing industries.The two kinds of actuators can replace each other in most fields,such as the point to point transmission occasion and some rotating occasions.However,there are very few research results about the advantages and disadvantages of two kinds of actuators under the same working conditions so far.In this paper,a novel comprehensive assessment method,named as overall life cycle comprehensive assessment(OLCCA),is proposed for comparison and assessment of pneumatic and electric actuators.OLCCA contains mechanical properties evaluation(MPE),life cycle cost analysis based on users(LCCABOU)and life cycle environmental impact analysis(LCEIA)algorithm in order to solve three difficult problems:mechanical properties assessment,cost analysis and environmental impact assessment about actuators.The mechanical properties evaluation of actuators is a multi-objective optimization problem.The fuzzy data quantification and information entropy methods are combined to establish MPE algorithm of actuators.Two kinds of pneumatic actuators and electric actuators with similar bearing capacity and similar work stroke were taken for example to verify the correctness of MPE algorithm.The case study of MPE algorithm for actuators verified its correctness.LCCABOU for actuators is also set up.Considering cost complex structure of pneumatic actuators,public device cost even method(PDCEM)is firstly presented to solve cost division of public devices such as compressors,aftercooler,receivers,etc.LCCABOU method is also effective and verified by the three groups of pneumatic actuators and electric actuators.Finally,LCEIA model of actuators is established for the environmental impact assessment of actuators.LCEIA data collection method and model establishment procedure for actuators are also put forward.With Simapro 7,LCEIA comparison results of six actuators can be obtained:Fossil fuels are the major environmental factor of pneumatic and electric actuators;Environmental impact of electric actuator is large than one of pneumatic actuator under the similar mechanical properties and working conditions of pneumatic and electric actuators.The results are correct and correspond with the actual mechanical properties of actuators.This paper proposes a comprehensive evaluation method of the actuators,which can solve the critical problem that similar electromechanical products are very difficult to be compared with each other from the angle of performance,cost and environment impact.

Objective Immediate physical exercise has been recommended for patients in the recovery phase to improve survival and quality of life(QOL)and reduce recurrence of disease.The new NCCN Guidelines for Survivorship also highlighted the role of exercise in post-cancer health,encouraging patients to perform light physical activity following treatment.The aim of our study is to effect of Tai Chi Chuan(TCC)on serotonin and cortisol for monitoring stress and QOL in post-treatment breast cancer patients.Methods Totally85 post-treatment breast cancer patients were enrolled in this study to observe the effects of practicing TCC on recovery,as well as stress and happiness which are indicators of QOL of in patients.Peripheral blood was drawn from study subjects to analyze the levels of serotonin,cortisol and high sensitive C-reactive protein(HSCRP)at baseline,and at 3,6 and 12 months of TCC practice.Blood was drawn from healthy subjects only at baseline.A QOL questionnaire was administered to study subjects at three time points throughout the study,and once for healthy controls.The data were processed by analysis of variance of repeated measurement.Results At 3,6 and 12 months time points following regular TCC exercise,WBC,RBC,hemoglobin in blood samples showed a statistically significant difference(F=161.55,172.14,289.73;all P=0.00);the level of serotonin(biomarker for well-being),cortisol(indicator of stress)and HS-CRP(biomarker for inflammation)showed a statistical improvement(F=307.46,182.85,102.23;all P=0.00).After 3,6 and 12 months of regular TCC exercise,according to the results of QOL questionnaire,the indicators including quality of sleep,perceived hunger,fatigue,contentment,stress and social interaction presented a significant difference(F=312.98,222.64,543.90,46.05,28.10,78.92,all P<0.05),while there was no statistical difference in life dissatisfaction(F=56.61,P=0.166)Conclusions TCC physical activity for post-treatment breast cancer patients improved QOL and overall well-being,leading to improved mental,physical and psychological functioning.Regulated levels of serotonin and cortisol mediated by TCC exercises are proved to be vital for continued good health.

The competition of surface and subsurface crack initiation induced failure is critical to understand very high cycle fatigue(VHCF)behavior,which necessitates the elucidation of the underlying mechanisms for the transition of crack initiation from surface to interior defects.Crack initiation potential in materials containing defects is investigated numerically by focusing on defect types,size,shape,location,and residual stress influences.Results show that the crack initiation potency is higher in case of serious property mismatching between matrix and defects,and higher strength materials are more sensitive to soft inclusions(elastic modulus lower than the matrix).The stress localization around inclusions are correlated to interior crack initiation mechanisms in the VHCF regime such as inclusion-matrix debonding at soft inclusions and inclusion-cracking for hard inclusions(elastic modulus higher than the matrix).It is easier to emanate cracks from the subsurface pores with the depth 0.7 times as large as their diameter.There exists an inclusion size independent region for crack incubation,outside which crack initiation will transfer from the subsurface soft inclusion to the interior larger one.As for elliptical inclusions,reducing the short-axis length can decrease the crack nucleation potential and promote the interior crack formation,whereas the long-axis length controls the site of peak stress concentration.The compressive residual stress at surface is helpful to shift crack initiation from surface to interior inclusions.Some relaxation of residual stress can not change the inherent crack initiation from interior inclusions in the VHCF regime.The work reveals the crack initiation potential and the transition among various defects under the influences of both intrinsic and extrinsic factors in the VHCF regime,and is helpful to understand the failure mechanism of materials containing defects under long-term cyclic loadings.

Blade vibration failure is one of the main failure modes of compressor wheel of turbocharger for vehicle application.The existing models for evaluating the reliability of blade vibration of compressor wheel are static,and can not reflect the relationship between the reliability of compressor wheel with blade vibration failure mode and the life parameter.For the blade vibration failure mode of compressor wheel of turbocharger,the reliability evaluation method is studied.Taking a compressor wheel of turbocharger for vehicle application as an example,the blade vibration characteristics and how they change with the operating parameters of turbocharger are analyzed.The failure criterion for blade vibration mode of compressor wheel is built with the Campbell diagram,and taking the effect of the dispersity of blade natural vibration frequency and randomness of turbocharger operating speed into account,time-dependent reliability models of compressor wheel with blade vibration failure mode are derived,which embody the parameters of blade natural vibration frequency,turbocharger operating speed,the blade number of compressor wheel,life index and minimum number of resonance,etc.Finally,the rule governing the reliability and failure rate of compressor wheel and the method for determining the reliable life of compressor with blade vibration is presented.A method is proposed to evaluate the reliability of compressor wheel with blade vibration failure mode time-dependently.

Influence of geometric and cutting parameters of cemented carbide cutting tool on reliability of cutting tool has become more and more mature,yet influence of its physical and material parameters on reliability is still blank.In view of this,cutting test and fatigue crack growth test of YT05 cemented carbide cutting tool are conducted to measure such data as the original crack size,growth size,times of impact loading,number and time of cutting tool in failure,and stress distribution of cutting tool is also obtained by simulating cutting process of tools.Mathematical models on dynamic reliability and dynamic reliability sensitivity of cutting tool are derived respectively by taking machining time and times of impact loading into account,thus change rules of dynamic reliability sensitivity to physical and material parameters can be obtained.Theoretical and experimental results show that sensitive degree on each parameter of tools increases gradually with the increase of machining time and times of impact loading,especially for parameters such as fracture toughness,shape parameter,and cutting stress.This proposed model solves such problems as how to determine the most sensitive parameter and influence degree of physical parameters and material parameters to reliability,which is sensitivity,and can provide theoretical foundation for improving reliability of cutting tool system.

基于沥青路面裂纹扩展行为,设计预切口小梁试件的疲劳试验,以模拟其复合裂纹扩展模式;以疲劳寿命指标来评价沥青混合料的抗裂性能,同时进行沥青混合料的低温弯曲试验和J积分试验,试验混合料采用4种低温性能差异显著的沥青胶结料.判别各项评价指标对试验混合料抗裂性能的鉴别程度,并分析沥青低温临界温度指标、低温弯曲试验指标、J积分试验指标与预切口小梁疲劳寿命的相关性.结果表明:以混合料疲劳性能为基准的混合料抗裂性能排序与沥青胶结料临界温度的排序一致,也与沥青混合料低温弯曲试验和J积分试验中能量指标的排序一致.

职业院校开展职业价值观教育,应从确立职业价值观的目标出发,立足职业道德,回答"做怎样的人":强化职业认知,成为"合格职业人";探求职业发展,培养"和谐职业人".分析职业院校学生智能、思维结构类型,厘清职业价值观教育具有的特质,强调其对主体的重视,对个体职业生活体验的重视.对作为一种"内心"评判的重视,作为一种对"职业生活"理解的重视,从而创设可以激活学生体验的情境和活动.探讨在回归职业生活、回归内心体验情镜下的职业价值观教育实施路径.