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1.
高应变低周疲劳的能量分析方法   总被引:2,自引:0,他引:2  
从疲劳过程中材料吸收的总应变能和每次循环的应力应变滞后环出发,推出了形如Coffin-Manson公式和Basquin公式的寿命预测表达式。实验验证结果表明,在高应变低寿命区,理论与实测的△εp-2Nf曲线相吻合。  相似文献   

2.
本文采用恒应变幅(△ε)低周疲劳试验方法,测定了高碳Patenting高强度钢丝和低碳LAHS钢丝的循环应力幅(△σ)和最大应力(σmax)与循环周次(N)之间的关系。研究了温形变处理对钢丝低周疲劳寿命的影响。得出,温形变处理可提高低周疲劳寿命30%~35%。对这类钢丝的低周疲劳损伤进行了评价。  相似文献   

3.
多向应力作用下的金属材料热疲劳问题.在70年代初,日本学者平修工,井上达 雄等人曾进行过研究,提出了用当量应变范围评价多向应力作用下的热疲劳寿命方法. 作者在此基础上.对合金材料GH36在较大应变范围下的热疲劳问题进行了研究。 试验机为热裂型.瞬时应力和应变用有限元法求出,然后定出裂纹萌生点的当量应变 范围。结果表明;在相同的当量应变范围,裂纹长度小于0.2mm;热疲劳寿命比当 量温度下的高温低周疲劳寿命低;当裂纹长度等于0.2mm,热疲劳寿命与当量温度 下的高温低周疲劳寿命相同。  相似文献   

4.
通过对 LY-12 CZ铝合金材料在常温、拉扭复合比例及非比例加载条件下循环特性及寿命的实验研究,得出了用 Mises等效应力幅值的峰值随积累应变增加的变化来描述非比例加载循环时硬(软)化规律是可行的,确认了可以用等效应变幅值e和最大剪应变平面上的正应变εn两个参数来描述非比例加载的疲劳寿命。  相似文献   

5.
多维应力状态下LD8铝合金高温低周疲劳寿命的评价   总被引:3,自引:2,他引:3  
采用LD8铝合金的圆柱形缺口试件进行了高温低周疲劳试验,并借助ADINA程序分析了缺口周围的多维应力和应变,探讨了多维疲劳寿命的评价方法,结果表明,当量应变范围和应变能密度都可作为评价疲劳寿命的有效参量。  相似文献   

6.
对两种新型中碳弹簧钢应变疲劳特性及其回火硬度影响进行了研究,并和中高碳弹簧钢60Si_2Mn进行了对比。结果表明:两个新型弹簧钢和60Si_2Mn都具有循环软化;在应变疲劳曲线(△ε/2~2N_f)上,弹性线和塑性线的交点随弹簧钢回火硬度的升高而向低循环寿命移动;在Monson-Coffin方程中的回归常数b和C与循环应变硬化指数n的关系大体符合b=-n/(1+5n),C=-1/(1+5n)。各钢的应变疲劳特性、组织特征和断口形貌之间有一定的对应关系。同样硬度下新钢较老钢有更高的过载抗力。  相似文献   

7.
塑性应变疲劳裂纹扩展研究进展   总被引:1,自引:0,他引:1  
介绍了两类循环J积分--Dowling“实用”△J定义与Tanaka等的积分△Jpath定义的研究现状,分析了其用于描述塑性应变疲劳裂纹扩展速率时的问题。  相似文献   

8.
本文根据某结合钢桁梁桥的荷载情况,取两种疲劳荷载(应力上限σmax相同,但应力幅△σ不同)在八种疲劳次数下对加载龄期较长的C50混凝土做了试验研究,分析了混凝土在疲劳荷载作用下的瞬时弹性模量Et、持续弹性模量Er及疲劳残余应变εr,并与加载龄期较短的C50混凝土试验结果进行了比较.由此说明了加载龄期对混凝土弹性模量和残余应变的影响.  相似文献   

9.
本文从疲劳应变能的角度推导出了应变-寿命关系式。通过测定常规机械性能,就可预测材料在不同应变幅下的低周疲劳寿命;讨论了低周疲劳抗力与常规机械性能之间的关系,指出了材料本身对低周疲劳行为的主要影响因素;提出了选择抗低周疲劳材料的基本原则。  相似文献   

10.
高温疲劳强度与J积分关系的探讨   总被引:1,自引:0,他引:1  
建立了时间依存性疲劳、循环数依存性疲劳和蠕变疲劳交互作用下裂纹扩展速度及 寿命的评价公式,并用灰铸铁的试验数据作了验证。结果表明,所建立的寿命法则对高 温低周疲劳和热疲劳都成立;其同相和C-P型试验点均落在同一条△Wc-Nf线上, 而异相和 P-C型的都落在△ Wf-Nf上;但若用 △ Jtot表征裂纹扩展,则可将高温 下不同类型的疲劳归纳到同一条△Wtot-Nf线上。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

15.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

16.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.  相似文献   

17.
以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.  相似文献   

18.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

19.
Quality traits in wheat (Triticum aestirum L.) were studied by quantitative trait locus (QTL) analysis in a recombinant inbred line (RIL) population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross (ChSh). Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.  相似文献   

20.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

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