T. Kusaka, Takanori Kono, Y. Nomura, Hiroki Wakabayashi
A novel experimental method was proposed for characterizing the compressive properties of composite materials under impact loading. Split Hopkinson pressure bar system was employed to carry out the dynamic compression tests. The dynamic stress-strain relations could be precisely estimated by the proposed method, where the ramped input, generated by the plastic deformation of a zinc buffer, was effective to reduce the oscillation of the stress field in the specimen. The longitudinal strain of gage area could be estimated from the nominal deformation of gage area, and consequently the failure process could be grasped in detail from the stress-strain relation. Finite element analysis was also carried out to confirm the validity of the proposed method. Numerical results demonstrated that the nonuniformity of the stress field could be negligible by using the ramped input. The dynamic compressive strength of a twilled-woven carbon-fiber/epoxy composite was slightly higher than the static compressive strength.
{"title":"Experimental Method for Dynamic Compression Behavior of Composite Laminates Using SHPB Technique","authors":"T. Kusaka, Takanori Kono, Y. Nomura, Hiroki Wakabayashi","doi":"10.2472/JSMS.63.362","DOIUrl":"https://doi.org/10.2472/JSMS.63.362","url":null,"abstract":"A novel experimental method was proposed for characterizing the compressive properties of composite materials under impact loading. Split Hopkinson pressure bar system was employed to carry out the dynamic compression tests. The dynamic stress-strain relations could be precisely estimated by the proposed method, where the ramped input, generated by the plastic deformation of a zinc buffer, was effective to reduce the oscillation of the stress field in the specimen. The longitudinal strain of gage area could be estimated from the nominal deformation of gage area, and consequently the failure process could be grasped in detail from the stress-strain relation. Finite element analysis was also carried out to confirm the validity of the proposed method. Numerical results demonstrated that the nonuniformity of the stress field could be negligible by using the ramped input. The dynamic compressive strength of a twilled-woven carbon-fiber/epoxy composite was slightly higher than the static compressive strength.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91528936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Relationship between Strength and Process Parameters in Friction Stir Spot Welded PVC Joint Fabricated Composite Material at Welded Region","authors":"Yohei Kurabe, Y. Miyashita, H. Hori","doi":"10.2472/JSMS.63.837","DOIUrl":"https://doi.org/10.2472/JSMS.63.837","url":null,"abstract":"","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77592254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper studies the stress waveform effect on low cycle fatigue life for three kinds of notched specimens at elevated temperature. Low cycle fatigue tests were carried out using circumferential notched specimens of SUS316FR stainless steel using fast-fast, slow-fast and hold-time stress waveforms at 923K. Neuber’s rule recommended in ASME Code Case was applied to estimate failure and crack initiation lives. Failure lives were underestimated by Neuber’s rule in ASME Code Case NH. Crack initiation lives under the fast-fast, slow-fast and hold-time stress waveforms were correlated within a factor of 4 scatter band by using modified Neuber’s equation in which the exponent of K t was changed from 2 to 1.2 in the combination with frequency modified fatigue life equation.
{"title":"Stress Waveform Effect on Low-Cycle Fatigue Life for SUS316FR Round Notched Bar and the Life Prediction","authors":"N. Hamada, M. Sakane, K. Motoie, H. Umeda","doi":"10.2472/JSMS.63.647","DOIUrl":"https://doi.org/10.2472/JSMS.63.647","url":null,"abstract":"This paper studies the stress waveform effect on low cycle fatigue life for three kinds of notched specimens at elevated temperature. Low cycle fatigue tests were carried out using circumferential notched specimens of SUS316FR stainless steel using fast-fast, slow-fast and hold-time stress waveforms at 923K. Neuber’s rule recommended in ASME Code Case was applied to estimate failure and crack initiation lives. Failure lives were underestimated by Neuber’s rule in ASME Code Case NH. Crack initiation lives under the fast-fast, slow-fast and hold-time stress waveforms were correlated within a factor of 4 scatter band by using modified Neuber’s equation in which the exponent of K t was changed from 2 to 1.2 in the combination with frequency modified fatigue life equation.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86811102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"高温環境下におけるSiN x /SiC y ナノ積層薄膜の自己き裂治癒挙動","authors":"正憲 中谷, 淳樹 西村, 聡 花木, 仁 内田","doi":"10.2472/JSMS.62.634","DOIUrl":"https://doi.org/10.2472/JSMS.62.634","url":null,"abstract":"","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75190401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"第12回コンクリート構造物の補修，補強，アップグレードシンポジウム","authors":"貴士 山本","doi":"10.2472/JSMS.62.231","DOIUrl":"https://doi.org/10.2472/JSMS.62.231","url":null,"abstract":"","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82684454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Cr-Mo-V鋼のクリープ中の非線形音響特性の変化と微細組織の関係","authors":"俊博 大谷, 祐紀 草なぎ, 優 石井","doi":"10.2472/JSMS.62.60","DOIUrl":"https://doi.org/10.2472/JSMS.62.60","url":null,"abstract":"","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81377182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Effects of crosslinked molecular structures in glassy epoxy networks on the nonlinear viscoelastic behavior have been studied in terms of strain-induced structural change. We prepared four epoxy glasses with different crosslink densities from the same epoxy precursor by controlling fractions of chain-extender and crosslinker in curing agents. The epoxy glasses were subjected to uniaxial compression at a temperature 18K below the glass transition temperature of each sample. With increasing crosslink density, initial elastic moduli and yield stresses decreased, whereas flow stresses appearing after the strain softening almost unchanged, except for the most tightly crosslinked sample show-ing lower flow stresses. Results of density measurement and DSC showed that an increase in the crosslink density made the glassy structures more unstable. These results show that unstable glassy structures due to constraints on segmental mobility introduced by crosslinked molecular structures lessen the initial elastic modulus and the yield stress. On the other hand, the variation of crosslink density had almost no effect on the flow stresses of the glasses. This observation presumably indicates that molecular crosslinks have little effect on the strain-induced structural change. When the crosslink density comes to quite high, however, the crosslinks are likely to start affecting the flow stress, i.e. strain-induced unstable glassy structures.
{"title":"Effect of Crosslink Density on Nonlinear Stress-Strain Behavior of Epoxy Glasses Subjected to Large Deformation","authors":"S. Yoshioka, Y. Yokoyama","doi":"10.2472/JSMS.62.22","DOIUrl":"https://doi.org/10.2472/JSMS.62.22","url":null,"abstract":"Effects of crosslinked molecular structures in glassy epoxy networks on the nonlinear viscoelastic behavior have been studied in terms of strain-induced structural change. We prepared four epoxy glasses with different crosslink densities from the same epoxy precursor by controlling fractions of chain-extender and crosslinker in curing agents. The epoxy glasses were subjected to uniaxial compression at a temperature 18K below the glass transition temperature of each sample. With increasing crosslink density, initial elastic moduli and yield stresses decreased, whereas flow stresses appearing after the strain softening almost unchanged, except for the most tightly crosslinked sample show-ing lower flow stresses. Results of density measurement and DSC showed that an increase in the crosslink density made the glassy structures more unstable. These results show that unstable glassy structures due to constraints on segmental mobility introduced by crosslinked molecular structures lessen the initial elastic modulus and the yield stress. On the other hand, the variation of crosslink density had almost no effect on the flow stresses of the glasses. This observation presumably indicates that molecular crosslinks have little effect on the strain-induced structural change. When the crosslink density comes to quite high, however, the crosslinks are likely to start affecting the flow stress, i.e. strain-induced unstable glassy structures.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89956734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, we focused on the principal stress value and direction in weld residual stress fields. We used specimens welded under three heat input conditions, and so the weld metal of each specimen had a different solidification structure. We evaluated the principal stress value and direction of the specimens by X-ray stress measurement. In the specimen welded under the smallest heat input condition, the weld metal showed a clear difference between the maximum principal stress and the minimum principal stress. However, in the specimen welded under the largest heat input condition, the maximum principal stress and the minimum principal stress were almost the same value. The principal stress direction changed significantly and shear stress occurred at the weld metal boundary in the specimens welded under the large heat input condition. In all specimens, the principal stress direction in the base metal changed. As conclusions, when the minimum and the maximum principal stress values were almost the same, the principal stress direction changed more noticeably. Additionally, due to the influence of the edge in the base metal, the principal stress direction changed significantly regardless of the welding condition.
{"title":"A Study on Changes of Principal Stress in Welding Residual Stress Fields","authors":"A. Tsuji, T. Hashimoto, S. Okano, M. Mochizuki","doi":"10.2472/JSMS.62.424","DOIUrl":"https://doi.org/10.2472/JSMS.62.424","url":null,"abstract":"In this study, we focused on the principal stress value and direction in weld residual stress fields. We used specimens welded under three heat input conditions, and so the weld metal of each specimen had a different solidification structure. We evaluated the principal stress value and direction of the specimens by X-ray stress measurement. In the specimen welded under the smallest heat input condition, the weld metal showed a clear difference between the maximum principal stress and the minimum principal stress. However, in the specimen welded under the largest heat input condition, the maximum principal stress and the minimum principal stress were almost the same value. The principal stress direction changed significantly and shear stress occurred at the weld metal boundary in the specimens welded under the large heat input condition. In all specimens, the principal stress direction in the base metal changed. As conclusions, when the minimum and the maximum principal stress values were almost the same, the principal stress direction changed more noticeably. Additionally, due to the influence of the edge in the base metal, the principal stress direction changed significantly regardless of the welding condition.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85259369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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