Pub Date : 1900-01-01DOI: 10.21741/9781644900338-24
S. G. Kulkarni, S. Ingole, M. Rathod, K. M. Rajan, R. Sinha, S. K. Nayak, N. P. N. Prakash, V. Dixit
{"title":"Improvement in Performance of Shaped Charge using Bimetallic Liner","authors":"S. G. Kulkarni, S. Ingole, M. Rathod, K. M. Rajan, R. Sinha, S. K. Nayak, N. P. N. Prakash, V. Dixit","doi":"10.21741/9781644900338-24","DOIUrl":"https://doi.org/10.21741/9781644900338-24","url":null,"abstract":"","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116566580","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}
Pub Date : 1900-01-01DOI: 10.21741/9781644900338-18
S. Morishima, T. Katayama, Z. Zhang, P. Suprobo, M. Yamaguchi, D. T. Setiamanah, A. Ogawa
Reducing spall damage is a major problem when designing blast-resistant concrete structures. This study was conducted to evaluate the influence of various material factors on the blast resistance of FRCC slabs under contact detonation. The contact detonation tests were carried out on polyvinyl alcohol fiber reinforced mortar (PVAFRM) slabs with four different shapes of PVA fibers and four different water-binder ratios (W/B) of the mortar matrix. Fly ash (type II) was used as admixture and the fluidity of the PVAFRM in its fresh state was varied using a superplasticizer and thickener. As a result, it was obtained that longer fiber is more effective to suppress spall if the fiber diameter is constant, and if the aspect ratio of fiber (lf/df) is constant, finer fibers are more effective to reduce spall. Moreover, the spall-reducing performance is reduced when the W/B value is too high or too low, and it is considered that there is an appropriate value of W/B that depends on the fiber shape. Introduction When designing blast-resistant concrete structures, reducing spall damage is a major problem. Spalling indicates the failure of reinforced concrete (RC) slabs due to contact detonation which caused by the tensile stress waves reflected from the backside of the slab. To preserve human life under such circumstances, the launch of concrete fragments accompanies the spalling needs to be prevented. The authors have verified the good spall-reducing performance of fiber reinforced cementitious composite (FRCC) slabs under contact detonation. However, a designing method for obtaining the required blast-resistant performance of the FRCC members has not been developed yet; one of the reasons for this is that it is difficult to obtain dynamic mechanical properties of FRCCs corresponding to this problem where the dominant strain rate is of the order of 10–10/s. Hence, it may be convenient to consider the spall-reducing performance of FRCC member as a material property of the FRCC. It can be obtained directly based on material factors such as fiber shape, water-binder ratio, and so on. This study was conducted to evaluate the influence of various material factors on the blast resistance of FRCC slabs under contact detonation; therefore, contact detonation tests were carried out on polyvinyl alcohol fiber reinforced mortar (PVAFRM) slabs with four different shapes of PVA fibers and four different water-binder ratios of the mortar matrix. Explosion Shock Waves and High Strain Rate Phenomena Materials Research Forum LLC Materials Research Proceedings 13 (2019) 103-108 https://doi.org/10.21741/9781644900338-18 104 Table 1 Materials used for PVAFRM. Cement Ordinary Portland cement; Density: 3.16 g/cm Admixture Fly ash (Type II); Density: 2.27 g/cm, Specific surface area: 3890 cm/g Fine aggregate Mountain sand; Surface-dried density: 2.56 g/cm, Water absorption: 2.29%, Maximum size: 2.5 mm, Fineness modulus: 2.58 Chemical admixture Superplasticizer (Polycarboxylic-acid
减少碎片损伤是设计抗爆混凝土结构的主要问题。研究了不同材料因素对FRCC板接触爆轰抗爆性能的影响。采用四种不同形状的聚乙烯醇纤维增强砂浆(PVAFRM)和四种不同的砂浆基质水胶比(W/B)对聚乙烯醇纤维增强砂浆(PVAFRM)板进行了接触爆轰试验。采用II型粉煤灰作为外加剂,采用高效减水剂和增稠剂改变PVAFRM在新鲜状态下的流动性。结果表明,在纤维直径一定的情况下,较长的纤维能更好地抑制剥落;在纤维长径比(lf/df)一定的情况下,较细的纤维能更好地抑制剥落。此外,W/B值过高或过低都会降低降屑性能,认为W/B有一个合适的值取决于纤维的形状。在设计抗爆混凝土结构时,减少小块损伤是一个主要问题。剥落是指钢筋混凝土板在接触爆轰作用下发生的破坏,而接触爆轰作用是由混凝土板背面反射的拉应力波引起的。为了在这种情况下保护人类的生命,需要防止混凝土碎片的发射伴随着剥落。试验验证了纤维增强胶凝复合材料(FRCC)板在接触爆轰作用下具有良好的减裂性能。然而,目前还没有一种设计方法来获得所需的FRCC构件的抗爆性能;其中一个原因是,在主导应变速率为10-10 /s数量级的情况下,很难获得相应的frcc动态力学性能。因此,可以方便地将FRCC构件的减碎性能作为FRCC的材料性能来考虑。可根据纤维形状、水胶比等材料因素直接得到。研究了不同材料因素对接触爆轰作用下FRCC板抗爆性能的影响;为此,对聚乙烯醇纤维增强砂浆(PVAFRM)板采用4种不同形状的聚乙烯醇纤维和4种不同的砂浆基质水胶比进行了接触爆轰试验。爆炸激波和高应变率现象材料研究论坛LLC材料研究学报第13期(2019)103-108 https://doi.org/10.21741/9781644900338-18 104表1 PVAFRM所用材料普通硅酸盐水泥;密度:3.16 g/cm掺合料粉煤灰(II型);密度:2.27 g/cm,比表面积:3890 cm/g细骨料山砂;表面干燥密度:2.56 g/cm,吸水率:2.29%,最大粒径:2.5 mm,细度模数:2.58化学外加剂高效减水剂(聚羧酸型);增稠剂(甲基纤维素型)短纤维PVA纤维(I型);密度:1.30 g/cm,尺寸:φ0.1 × 12mm,抗拉强度:1200mpa,拉伸弹性模量:28gpa PVA纤维(II型);密度:1.30 g/cm,尺寸:φ0.2 × 12mm,抗拉强度:975mpa,拉伸弹性模量:27gpa PVA纤维(III型);密度:1.30 g/cm,尺寸:φ0.2 × 18mm,抗拉强度:975mpa,拉伸弹性模量:27gpa PVA纤维(IV型);密度:1.30 g/cm,尺寸:φ0.2 × 24 mm,抗拉强度:975 MPa,抗拉弹性模量:27 GPa表2 PVAFRM的混合配比及静态力学性能。纤维类型Vf [%] W / B [%] FA / B [%] S / B[%]单位重量(公斤/米)Sp / B[%]流γ(kN / m)σB (MPa) E (GPa)ε有限公司(μ)σf (MPa) Bσ
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Pub Date : 1900-01-01DOI: 10.21741/9781644900338-22
A. Aggarwal, Sd Tyagi, B. B. Sherpa, D. Pal, Sandeep Kumar, A. Upadhyay
Explosive welding is a solid state welding process in which two similar or different materials are claded with the help of explosive energy. The high pressure generated during the process helps to achieve the interatomic metallurgical bonding in the two materials. In this research work, 5 mm aluminum plate was cladded with 20 mm mild steel for plate length of 300 mm x100 mm. Here parallel plate explosive welding set-up configuration using low VoD explosive consisting of mixture of Trimonite-1 and common salt was used. The interface joints were analyzed using optical inverted metallurgical microscope, SEM and Vickers Micro-hardness. It was observed that the value of micro-hardness at the interface was high as compared to the parent materials and decreased as we move away from the interface on both the sides. The optical and the SEM analysis showed straight morphology at most of the welded area. Al-MS plates were successfully welded using this low VoD explosive. Introduction Composite material with good corrosion resistant as well as bond strength is one of the prime needs of any industry for their respective work application. Explosive welding is a well known defined solid state weld process, where two plates are claded with the help of explosive energy in which flyer plate is accelerated towards the base plate and at the interface a very high pressure order of magnitude 10 Mbar is generated followed by jet phenomenon[1]. Jet phenomenon is one of the important conditions for welding which occurs at the collision point in which it removes the oxide layer and provide clean mating surface free of contamination. This is attained by high pressure and kinetic energy deposited during the welding process[2]. Jet process helps atoms of two materials to meet at interatomic distance and form a strong metallurgical bond, where high temperature is obtained followed by rapid cooling in order of 10k/s[3]. Beside this, for weld to occur the pressure should be sufficient high and for sufficient length of time to achieve the bond formation. In explosive welding, pressure generated exceeds the yield strength of both the materials and which act as fluid at the collision point. It is a critical joining process where different parameters such as collision velocity, flyer plate velocity, VoD of explosive plays a very important role in formation of good bond[2] [4]. Many researchers have worked on this process using different material combination with variable explosive properties [5] [6] [7]. Aluminum is a light and corrosion resistant material having vast application in the naval and oil industries. The challenge of joining comes due to difference in chemical, physical properties as well as low solubility of iron in aluminum. Different means have been used to join this combination such as magnetic pressure Explosion Shock Waves and High Strain Rate Phenomena Materials Research Forum LLC Materials Research Proceedings 13 (2019) 128-133 https://doi.org/10.21741/978164490
{"title":"Explosive Welding of Al-MS Plates and its Interface Characterization","authors":"A. Aggarwal, Sd Tyagi, B. B. Sherpa, D. Pal, Sandeep Kumar, A. Upadhyay","doi":"10.21741/9781644900338-22","DOIUrl":"https://doi.org/10.21741/9781644900338-22","url":null,"abstract":"Explosive welding is a solid state welding process in which two similar or different materials are claded with the help of explosive energy. The high pressure generated during the process helps to achieve the interatomic metallurgical bonding in the two materials. In this research work, 5 mm aluminum plate was cladded with 20 mm mild steel for plate length of 300 mm x100 mm. Here parallel plate explosive welding set-up configuration using low VoD explosive consisting of mixture of Trimonite-1 and common salt was used. The interface joints were analyzed using optical inverted metallurgical microscope, SEM and Vickers Micro-hardness. It was observed that the value of micro-hardness at the interface was high as compared to the parent materials and decreased as we move away from the interface on both the sides. The optical and the SEM analysis showed straight morphology at most of the welded area. Al-MS plates were successfully welded using this low VoD explosive. Introduction Composite material with good corrosion resistant as well as bond strength is one of the prime needs of any industry for their respective work application. Explosive welding is a well known defined solid state weld process, where two plates are claded with the help of explosive energy in which flyer plate is accelerated towards the base plate and at the interface a very high pressure order of magnitude 10 Mbar is generated followed by jet phenomenon[1]. Jet phenomenon is one of the important conditions for welding which occurs at the collision point in which it removes the oxide layer and provide clean mating surface free of contamination. This is attained by high pressure and kinetic energy deposited during the welding process[2]. Jet process helps atoms of two materials to meet at interatomic distance and form a strong metallurgical bond, where high temperature is obtained followed by rapid cooling in order of 10k/s[3]. Beside this, for weld to occur the pressure should be sufficient high and for sufficient length of time to achieve the bond formation. In explosive welding, pressure generated exceeds the yield strength of both the materials and which act as fluid at the collision point. It is a critical joining process where different parameters such as collision velocity, flyer plate velocity, VoD of explosive plays a very important role in formation of good bond[2] [4]. Many researchers have worked on this process using different material combination with variable explosive properties [5] [6] [7]. Aluminum is a light and corrosion resistant material having vast application in the naval and oil industries. The challenge of joining comes due to difference in chemical, physical properties as well as low solubility of iron in aluminum. Different means have been used to join this combination such as magnetic pressure Explosion Shock Waves and High Strain Rate Phenomena Materials Research Forum LLC Materials Research Proceedings 13 (2019) 128-133 https://doi.org/10.21741/978164490","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133291567","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}
Pub Date : 1900-01-01DOI: 10.21741/9781644900338-11
S. Singh, H. N. Behera, D. Pal, A. Gupta
The fragment safety distance is an important requirement for test and evaluation of the munition stores in the field trials. It determines the area to be cleared or evacuated before conduct of any trial activity. In this paper, theoretical and experimental work is carried out for establishing the explosive parameters and its interaction with the metallic casing. High explosives are used for controlled fragmentation to generate specific–size-and-weight fragments with lower velocity. Empirical relationship based on high strain rate and Gurney energy criteria were applied and optimized. Two prototypes having two different type explosive filling were fabricated to generate the fragment data. This enables to determine the safety distance useful for conducting trials in small ranges with required safety. The experimental data reveals that 90% fragments of a definite shape and size have been generated. The recorded fragment velocity was of the order of 250 to 400 m/s. Based on these data, safety distance was calculated and found to be about 400 m. Experimentally, fragments were recovered and found up to 130m from the point of burst.
{"title":"Experimental and Theoretical Study of Fragment Safety Distance of Fragmenting Munitions","authors":"S. Singh, H. N. Behera, D. Pal, A. Gupta","doi":"10.21741/9781644900338-11","DOIUrl":"https://doi.org/10.21741/9781644900338-11","url":null,"abstract":"The fragment safety distance is an important requirement for test and evaluation of the munition stores in the field trials. It determines the area to be cleared or evacuated before conduct of any trial activity. In this paper, theoretical and experimental work is carried out for establishing the explosive parameters and its interaction with the metallic casing. High explosives are used for controlled fragmentation to generate specific–size-and-weight fragments with lower velocity. Empirical relationship based on high strain rate and Gurney energy criteria were applied and optimized. Two prototypes having two different type explosive filling were fabricated to generate the fragment data. This enables to determine the safety distance useful for conducting trials in small ranges with required safety. The experimental data reveals that 90% fragments of a definite shape and size have been generated. The recorded fragment velocity was of the order of 250 to 400 m/s. Based on these data, safety distance was calculated and found to be about 400 m. Experimentally, fragments were recovered and found up to 130m from the point of burst.","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133451644","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}
Pub Date : 1900-01-01DOI: 10.21741/9781644900338-7
Yohei Shinshi, M. Miyazaki, Keisuke Yokoya
Aluminum tubes are energy-efficient absorbing components and are widely used for framework and reinforcement materials of structures. The effects of the axial length and crosssectional shape on the deformation behavior were investigated. Regarding the axial length, it has changed only to a certain length, and there are few studies on it. This paper deals with the influence of axial length. Also, when an impact is actually applied to the square tube, the impact in the oblique direction must also be taken into consideration. Therefore, the deformation behavior was analyzed by applying impact to the square tube from various angles other than the axial direction. An analysis of the dynamic deformation process of the polygonal tube was made using a finite element method. The results show that the load reached the peak immediately after the weight hit the square tube, then declined gently. The same tendency was obtained even if the axial length was changed. However, as the axial length became longer, the displacement taken to reach the peak load increased. As for the impact in the oblique direction, the peak load was small as compared with the axial direction. The deformation of square tube did not buckle in whole but only partially at any length. Introduction Square tubes have been used for framework and reinforcement members of structures.There are many studies on circular tubes, and deformation behaviors have been studied by static and dynamic compression tests [1]. Previous studies have shown that square tubes have a role of absorbing impact energy by crushing under pressure in the axial direction at the time of a collision [2]. Aluminum alloy has a Young’s modulus that is one-third that of commonly used steel materials, giving it the disadvantage of low rigidity. In addition, the whole buckles become large when thickness is increased, and causing axial compression deformation, which cannot effectively absorb collision energy[3].The tubular bodies with polygonal tubes and cellular cross sections have been studied as a means to effectively absorb energy [4]. Additionally, an influence of axial length on dynamic axially compressed aluminum tubes is being considered [57].It is known that elastic deformation occurs in the entire square tube prior to plastic deformation when the square tube deforms. Since this is periodic and wavy, it seems that the axial length will have a large influence. In a previous study, deformation behaviors up to 500 mm in length have been considered [8]. The purpose of this paper is to discuss, the deformation behavior of dynamic axial compression of an aluminum square tube of axial lengths of 500 mm, 750mm and 1000 mm. Also, when an impact is applied to the tube, the impact in the oblique direction must also be taken into consideration. Therefore, for comparison with the axial compression, deformation behavior of aluminum square tube under oblique impact loading was considered. Explosion Shock Waves and High Strain Rate Pheno
铝管是一种节能吸波材料,广泛应用于结构的框架和加固材料。研究了轴向长度和截面形状对变形行为的影响。轴向长度仅变化为一定长度,研究较少。本文讨论了轴向长度的影响。此外,当实际对方管施加冲击时,还必须考虑斜向的冲击。因此,通过对方管施加除轴向外的不同角度的冲击来分析其变形行为。采用有限元法对多角形管的动态变形过程进行了分析。结果表明:载荷在重物撞击方管后立即达到峰值,然后缓慢下降;即使改变轴向长度,也有相同的趋势。然而,随着轴向长度的增加,达到峰值荷载所需的位移增加。对于斜向冲击,峰值载荷相对于轴向冲击较小。方管的变形在任何长度上都不发生整体屈曲,而只是部分屈曲。方管已广泛应用于结构的框架和配筋构件。对圆管的研究较多,通过静、动压缩试验研究了圆管的变形行为[1]。已有研究表明,方形管在碰撞时具有轴向受压破碎吸收冲击能的作用[2]。铝合金的杨氏模量是常用钢材料的三分之一,因此具有刚性低的缺点。此外,随着厚度的增加,整体屈曲变大,产生轴向压缩变形,不能有效吸收碰撞能量[3]。已经研究了具有多角形管和细胞截面的管状体作为有效吸收能量的手段[4]。此外,还考虑了轴向长度对动态轴向压缩铝管的影响[57]。众所周知,方管变形时,整个方管的弹性变形先于塑性变形。由于这是周期性和波浪式的,因此轴向长度似乎会有很大的影响。在之前的研究中,已经考虑了长度达500mm的变形行为[8]。本文讨论了轴向长度为500mm、750mm和1000mm的铝方管在动态轴压下的变形行为。此外,当对管施加冲击时,还必须考虑斜向的冲击。因此,为了与轴向压缩进行比较,考虑了铝方管在斜向冲击载荷下的变形行为。爆炸激波与高应变率现象材料研究论坛LLC材料研究学报13 (2019)41-46 https://doi.org/10.21741/9781644900338-7 42数值分析通过非线性结构分析程序(Marc 2018)和前后处理程序(Mentat 2018)进行分析。解析模型的示例如图1所示。试样为铝管(A6063-T5)。材料性能如表1所示。对于轴向长度l,分别在20000、30000、40000双线性四节点壳单元上离散方形管(l = 500mm、750mm和1000mm)。在斜向分析中,取重物与方管冲击边缘夹角θ= 10度。分析模型示意图如图2所示。图1方管(l = 500mm)解析模型。图2重物撞击角(θ= 10°)。除在冲击边的轴向外,管边缘上的节点均固定。重量(80 × 80 × 20毫米,15公斤)是一个非离散的三维,八节点,一阶,等参元素。将变形管视为符合von-Mises屈服条件的各向同性材料,由于铝的应变速率影响小于铁等其他材料[9],流变应力-应变关系如式(1)所示。X Y Z θ铝重量
{"title":"Deformation Behavior of a Polygonal Tube under Oblique Impact Loading","authors":"Yohei Shinshi, M. Miyazaki, Keisuke Yokoya","doi":"10.21741/9781644900338-7","DOIUrl":"https://doi.org/10.21741/9781644900338-7","url":null,"abstract":"Aluminum tubes are energy-efficient absorbing components and are widely used for framework and reinforcement materials of structures. The effects of the axial length and crosssectional shape on the deformation behavior were investigated. Regarding the axial length, it has changed only to a certain length, and there are few studies on it. This paper deals with the influence of axial length. Also, when an impact is actually applied to the square tube, the impact in the oblique direction must also be taken into consideration. Therefore, the deformation behavior was analyzed by applying impact to the square tube from various angles other than the axial direction. An analysis of the dynamic deformation process of the polygonal tube was made using a finite element method. The results show that the load reached the peak immediately after the weight hit the square tube, then declined gently. The same tendency was obtained even if the axial length was changed. However, as the axial length became longer, the displacement taken to reach the peak load increased. As for the impact in the oblique direction, the peak load was small as compared with the axial direction. The deformation of square tube did not buckle in whole but only partially at any length. Introduction Square tubes have been used for framework and reinforcement members of structures.There are many studies on circular tubes, and deformation behaviors have been studied by static and dynamic compression tests [1]. Previous studies have shown that square tubes have a role of absorbing impact energy by crushing under pressure in the axial direction at the time of a collision [2]. Aluminum alloy has a Young’s modulus that is one-third that of commonly used steel materials, giving it the disadvantage of low rigidity. In addition, the whole buckles become large when thickness is increased, and causing axial compression deformation, which cannot effectively absorb collision energy[3].The tubular bodies with polygonal tubes and cellular cross sections have been studied as a means to effectively absorb energy [4]. Additionally, an influence of axial length on dynamic axially compressed aluminum tubes is being considered [57].It is known that elastic deformation occurs in the entire square tube prior to plastic deformation when the square tube deforms. Since this is periodic and wavy, it seems that the axial length will have a large influence. In a previous study, deformation behaviors up to 500 mm in length have been considered [8]. The purpose of this paper is to discuss, the deformation behavior of dynamic axial compression of an aluminum square tube of axial lengths of 500 mm, 750mm and 1000 mm. Also, when an impact is applied to the tube, the impact in the oblique direction must also be taken into consideration. Therefore, for comparison with the axial compression, deformation behavior of aluminum square tube under oblique impact loading was considered. Explosion Shock Waves and High Strain Rate Pheno","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121162414","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}
Pub Date : 1900-01-01DOI: 10.21741/9781644900338-15
S. Ihara, T. Hasebe
{"title":"FTMP-Based Quantitative Evaluations for Dynamic Behavior of Dislocation Wall Structures","authors":"S. Ihara, T. Hasebe","doi":"10.21741/9781644900338-15","DOIUrl":"https://doi.org/10.21741/9781644900338-15","url":null,"abstract":"","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123670354","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}
Pub Date : 1900-01-01DOI: 10.21741/9781644900338-13
A. Mori
In explosive welding, it is known well that the collision angle and collision velocity are the important parameters to achieve good welding. In addition, generations of a metal jet and the interfacial waves are important for the explosive welding conditions. To know the parameters and the collision conditions, the optical observation and the numerical simulation for the oblique collision using a powder gun were done by the authors. A metal jet was observed clearly by using a powder gun and wavy interface was generated without the intermetallic layer for the reactive materials by controlling the welding conditions. In this investigation, the results of the optical observations and the numerical analysis for similar and dissimilar material combinations were reported. Introduction Explosive welding technique is known well as the welding method to weld strongly for the two metal plates of similar and/or dissimilar material combinations. In explosive welding technique, a metal flyer plate is accelerated by the detonation of explosive and is collided to another metal plate (base plate) with a certain angle at high velocity. A good welding is achieved with generating the interfacial waves in the welded interface and the metal jet at the collision point when the velocity and the angle collided are within the suitable range [1, 2]. Therefore, to achieve the optimal welding conditions for the difficult-to-weld materials, it is necessary to know the parameters and the collision phenomena, such as the metal jet generations and the interfacial waves. The mechanism of interfacial waves and the metal jet generation have been studied theoretically and/or numerically by many researchers [3-5]. Onzawa et al. [6] reported about the characteristics of metal jet generated by the collision of similar and dissimilar metals set on parallel and angular arrangement using a high-speed streak camera. The observation for the metal jet generation is difficult by the optical observation system because the detonation gas spreads out rapidly with the high velocity which is faster than the flying velocity of metal. From the weldability window proposed by Wittman [7] and Deribas [8], claddings same as explosive welding can be obtained when a metal plate collides obliquely at high velocity. To know the inclined collision, same as the phenomena of explosive welding, a powder gun was applied to observe the high-speed oblique collision, which is same as the phenomena of explosive welding, without the influence of detonation gas. And the numerical simulation using SPH solver in ANSYS AUTODYN software was used to understand the material behavior in the high-speed oblique collision, comparing with the experimental results. Explosion Shock Waves and High Strain Rate Phenomena Materials Research Forum LLC Materials Research Proceedings 13 (2019) 74-78 https://doi.org/10.21741/9781644900338-13 75 Experimental Procedure Experimental setup to observe the high-speed oblique collision is shown
{"title":"Observation for the High-Speed Oblique Collision of Metals","authors":"A. Mori","doi":"10.21741/9781644900338-13","DOIUrl":"https://doi.org/10.21741/9781644900338-13","url":null,"abstract":"In explosive welding, it is known well that the collision angle and collision velocity are the important parameters to achieve good welding. In addition, generations of a metal jet and the interfacial waves are important for the explosive welding conditions. To know the parameters and the collision conditions, the optical observation and the numerical simulation for the oblique collision using a powder gun were done by the authors. A metal jet was observed clearly by using a powder gun and wavy interface was generated without the intermetallic layer for the reactive materials by controlling the welding conditions. In this investigation, the results of the optical observations and the numerical analysis for similar and dissimilar material combinations were reported. Introduction Explosive welding technique is known well as the welding method to weld strongly for the two metal plates of similar and/or dissimilar material combinations. In explosive welding technique, a metal flyer plate is accelerated by the detonation of explosive and is collided to another metal plate (base plate) with a certain angle at high velocity. A good welding is achieved with generating the interfacial waves in the welded interface and the metal jet at the collision point when the velocity and the angle collided are within the suitable range [1, 2]. Therefore, to achieve the optimal welding conditions for the difficult-to-weld materials, it is necessary to know the parameters and the collision phenomena, such as the metal jet generations and the interfacial waves. The mechanism of interfacial waves and the metal jet generation have been studied theoretically and/or numerically by many researchers [3-5]. Onzawa et al. [6] reported about the characteristics of metal jet generated by the collision of similar and dissimilar metals set on parallel and angular arrangement using a high-speed streak camera. The observation for the metal jet generation is difficult by the optical observation system because the detonation gas spreads out rapidly with the high velocity which is faster than the flying velocity of metal. From the weldability window proposed by Wittman [7] and Deribas [8], claddings same as explosive welding can be obtained when a metal plate collides obliquely at high velocity. To know the inclined collision, same as the phenomena of explosive welding, a powder gun was applied to observe the high-speed oblique collision, which is same as the phenomena of explosive welding, without the influence of detonation gas. And the numerical simulation using SPH solver in ANSYS AUTODYN software was used to understand the material behavior in the high-speed oblique collision, comparing with the experimental results. Explosion Shock Waves and High Strain Rate Phenomena Materials Research Forum LLC Materials Research Proceedings 13 (2019) 74-78 https://doi.org/10.21741/9781644900338-13 75 Experimental Procedure Experimental setup to observe the high-speed oblique collision is shown ","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"136 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115881418","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}
Pub Date : 1900-01-01DOI: 10.21741/9781644900338-16
M. Nikawa, T. Shibuya, M. Yamashita
Similar or dissimilar metallic sheets were joined at their edges by the original impact joining method developed by one of the authors. Surface layers of both sheet edges activated by high-speed shear are immediately contacted with sliding motion in the joining process. The whole processing time is within a few milliseconds. The materials tested were mild steel and titanium sheets. Drop-weight impact testing machine was used. Joining performance of the fabricated sheets was evaluated by tensile test, etc. The joining was not available all over the thickness between sheets, in which sharp notch was observed near both sheet surfaces. The central portion was successfully joined without cavity. The joined specimen of mild steel and titanium was sliced to remove surfaces with such notch. Fracture occurs at the part of mild steel whose strength is lower, then the joining boundary was not damaged. Introduction It is well known that time and temperature effects have important role in solid state joining by atomic diffusion at elevated temperature. On the other hand, under cold condition, if the surface expansion is relatively large, two metal parts can join at the newly created surface, in which the brittle oxidized surface layer fractures. Joining strength in solid state welding was found to be approximately equal to the normal applied stress during the process in the absence of oxide films for the case of aluminum welded together in 1970 [1]. The film theory of such kind of welding or bonding was established, in which roll bonding was applied in 1983 [2]. Recently the film theory was used to derive a model that quantifies the relevance of these parameters to the weld strength [3]. Cold bonding may have a potential for recycling scrap aluminum [4]. The diffusion bonding is usually achieved by very high compressive stress with large plastic deformation. The shape drastically changes from the initial one and the joining strength also depends on the initial surface condition. Surface treatment is necessary for removal of the dirty surface layer. Experimental results in diffusion bonding were summarized for various metals including superplastic alloys [5]. Joining of different metals were tested [6] and experiments were carried out using super plastic materials [7, 8]. Hot isostatic pressing was also effective for the diffusion bonding of the nickel powder onto alumina tubing [9]. Divergent extrusion was used for bonding of aluminum by means of two opposing punches and finite element simulations was conducted [10]. However, the method requires very special conditions in temperature, atmosphere, surface treatment, etc. and they are very time consuming. One of the authors proposed a novel joining method for sheet metal [11]. The edge of the sheet is joined to another edge, where the sheet thickness is unchanged, because the plates are not plastically compressed. In the present study, the materials are mild steel and pure titanium sheets. Main objectives are t
相似或不同的金属板在其边缘连接由作者之一开发的原始冲击连接方法。在连接过程中,由高速剪切激活的两片板材边缘的表层立即发生滑动运动接触。整个处理时间在几毫秒内。测试的材料是低碳钢和钛板。采用落锤冲击试验机。通过拉伸试验等评价了所制备板材的连接性能。在板材之间的所有厚度上都没有连接,在两个板材表面附近观察到尖锐的缺口。中心部分连接成功,无空腔。将低碳钢与钛的接合试样进行切片,去除表面上的缺口。断裂发生在低碳钢强度较低的部分,连接边界未受到破坏。众所周知,时间和温度效应在原子高温扩散固相连接中起着重要的作用。另一方面,在冷条件下,如果表面膨胀较大,则两个金属部件可以在新形成的表面连接,脆性氧化表面层在此断裂。1970年发现,在没有氧化膜的情况下,固态焊接中的连接强度近似等于铝焊接过程中的正常施加应力[1]。这种焊接或粘接的薄膜理论是在1983年建立的,其中采用了辊焊[2]。最近,薄膜理论被用于导出一个模型,该模型量化了这些参数与焊缝强度的相关性[3]。冷键合可能具有回收废铝的潜力[4]。扩散连接通常是通过非常高的压应力和大的塑性变形来实现的。形状与初始形状相比发生了巨大的变化,连接强度也取决于初始表面条件。表面处理是必要的,以去除脏的表面层。综述了包括超塑性合金在内的各种金属的扩散连接实验结果[5]。对不同金属的连接进行了测试[6],并使用超塑性材料进行了实验[7,8]。热等静压对镍粉在氧化铝管上的扩散键合也是有效的[9]。采用辐散挤压法对铝材进行两对冲接合,并进行有限元模拟[10]。然而,该方法在温度、气氛、表面处理等方面需要非常特殊的条件,而且非常耗时。有作者提出了一种新的钣金连接方法[11]。板材的边缘连接到另一个边缘,其中板材厚度不变,因为板材没有塑料压缩。在本研究中,材料是低碳钢和纯钛板。主要目的是观察工具和材料在装置中的运动,并通过拉伸和弯曲试验,检查爆炸冲击波和高应变率现象materials Research Forum LLC materials Research Proceedings 13 (2019) 91-96 https://doi.org/10.21741/9781644900338-16 92不同材料组成的板材的变形性能。并用元素分析检查了边界。冲击连接装置如图1所示。该装置由落锤的冲击力驱动。质量为22 kg,撞击速度为10 m/s。下片材的左半部分由反冲器支撑,反冲器通过压缩圆管(A6061,直径12mm,壁厚1mm)给予反作用力。A冲头上缘受到冲击,此时开始同步剪切。上剪切面滑动以适应下剪切面。运动在规定的位置停止。该装置安装在预压缩的低弹性橡胶上,避免受力过大造成损坏。试验材料为1.0或3.2 mm厚的低碳钢SPC, 1.0或3.0 mm厚的纯钛TP340。拉伸强度分别为303、317和427、401 MPa。滑动阶段重叠长度变化较大。图1实验设置连接装置中工具与片材的运动通过高速摄像机观察工具与片材的运动,同时进行TP340(上试样)与SPC(下试样)的连接。渐进图如图2所示。在t: 87.7 μs和439 μs时捕获了SPC的剪切变形和断裂。SPC左半段向下移动,TP340剪切断裂后也向下移动。TP340在2456 μs处出现,两种材料的边缘在3018 μs处以规定的重叠长度相互滑动。滑动阶段在3333 μs处终止。
{"title":"Impact Joining of Metallic Sheets and Evaluation of its Performance","authors":"M. Nikawa, T. Shibuya, M. Yamashita","doi":"10.21741/9781644900338-16","DOIUrl":"https://doi.org/10.21741/9781644900338-16","url":null,"abstract":"Similar or dissimilar metallic sheets were joined at their edges by the original impact joining method developed by one of the authors. Surface layers of both sheet edges activated by high-speed shear are immediately contacted with sliding motion in the joining process. The whole processing time is within a few milliseconds. The materials tested were mild steel and titanium sheets. Drop-weight impact testing machine was used. Joining performance of the fabricated sheets was evaluated by tensile test, etc. The joining was not available all over the thickness between sheets, in which sharp notch was observed near both sheet surfaces. The central portion was successfully joined without cavity. The joined specimen of mild steel and titanium was sliced to remove surfaces with such notch. Fracture occurs at the part of mild steel whose strength is lower, then the joining boundary was not damaged. Introduction It is well known that time and temperature effects have important role in solid state joining by atomic diffusion at elevated temperature. On the other hand, under cold condition, if the surface expansion is relatively large, two metal parts can join at the newly created surface, in which the brittle oxidized surface layer fractures. Joining strength in solid state welding was found to be approximately equal to the normal applied stress during the process in the absence of oxide films for the case of aluminum welded together in 1970 [1]. The film theory of such kind of welding or bonding was established, in which roll bonding was applied in 1983 [2]. Recently the film theory was used to derive a model that quantifies the relevance of these parameters to the weld strength [3]. Cold bonding may have a potential for recycling scrap aluminum [4]. The diffusion bonding is usually achieved by very high compressive stress with large plastic deformation. The shape drastically changes from the initial one and the joining strength also depends on the initial surface condition. Surface treatment is necessary for removal of the dirty surface layer. Experimental results in diffusion bonding were summarized for various metals including superplastic alloys [5]. Joining of different metals were tested [6] and experiments were carried out using super plastic materials [7, 8]. Hot isostatic pressing was also effective for the diffusion bonding of the nickel powder onto alumina tubing [9]. Divergent extrusion was used for bonding of aluminum by means of two opposing punches and finite element simulations was conducted [10]. However, the method requires very special conditions in temperature, atmosphere, surface treatment, etc. and they are very time consuming. One of the authors proposed a novel joining method for sheet metal [11]. The edge of the sheet is joined to another edge, where the sheet thickness is unchanged, because the plates are not plastically compressed. In the present study, the materials are mild steel and pure titanium sheets. Main objectives are t","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115418575","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}
Pub Date : 1900-01-01DOI: 10.21741/9781644900338-1
Y. Kusuhara, K. Fujiwara, F. Kawashima, S. Maeda, R. Nanba
When flammable gases confined or compressed in closed space such as metal cases or shells accidentally combusted, the deflagration could be generated and building up to detonation might cause intensive explosion. High energy density has been pursued in some industrial products or in some manufacturing processes, while the risk of troubles is increasing. Generally the combustion transitions to detonation in highly turbulent flows and takes some buildup time or propagation length. But in the complicated and closed space geometry such as the structure of compressors there are many interactions among compressive wave and rigid surface, and then the transition to detonation frequently has been observed. The product design considering the transition phenomena and reducing the risk of explosions is required in high energy fields. In this study detonations of flammable gas in the high pressure vessel that has spaces linked with narrow curved path were observed and simulated numerically. A high speed camera was used to observe the flame, and the history data were acquired from pressure gauges. In the simulation, XiFoam mounted in Open FOAM was used as the base code. From the visual comparison between the results of the experiment and the simulation, it was shown that turbulent burning velocity suddenly increases and the pressure exceeds a certain value when combustion transition to detonation. These criteria is useful for the design of interior structure of high pressure facilities.
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Pub Date : 1900-01-01DOI: 10.21741/9781644900338-8
A. Hatta, Y. Kajiro
Magnetic pressure seam welding has attracted attention as a new joining method for aluminum thin plates. Magnetic pressure seam welding is a collision welding process, utilizing electromagnetic force as the acceleration mechanism. The electromagnetic seam welding is a method of abruptly adding a high density magnetic flux around a metal material and utilizing the generated electromagnetic force to deform the thin plate at high speed and pressure welding. This paper deal with the deformation behavior of parallel aluminum seam welded aluminum sheet. Numerical analysis of the dynamic deformation process of the metal plate is performed by the finite element method. The sample used for this analysis is assumed to be a thin plate made of aluminum (A1050-H24, width100mm, thickness 1mm) and composed of quadrilateral elements of plane strain. The experimental results show that the collision speed between the aluminum plates is sufficiently reproduced. The impact point velocity between the aluminum plate surfaces was very high at the initial collision point but decreased continuously during welding. It was also found that the smaller the gap is, the faster the collision point moving speed becomes. Introduction Aluminum has higher electrical conductivity and thermal conductivity than iron, so welding is difficult due to low heating efficiency. In previous studies, there is a report on the magnetic pressure seam welding method [1]-[14]. Magnetic pressure seam welding is a collision welding process similar to explosive welding and utilizes electromagnetic force as an acceleration mechanism. Magnetic pressure seam welding accelerates and collides a certain metal plate (flyer plate) to another stationary metal plate (parent plate) by using electromagnetic force. When an impulse current from a capacitor bank passes through a flat one-turn coil, a magnetic flux is instantaneously generated in the coil. The eddy currents are induced in insulated flyer plate in the coil. In magnetic pressure parallel seam welding, one-turn coils are arranged in parallel. A part of flyer plate along the longitudinal direction of the coil bulged toward a parent plate, then flyer plate collided and was welded to a parent plate. At the time of the high-speed collision, metal jets are emitted in the welding interface of the specimen [7]. The collision point velocity and collision angle are determined by the primary and induced electromagnetic force. True metallic bonding is achieved at the mating interface if contact takes place above an appropriate collision point velocity and collision angle [15]. The purpose of this paper is to discuss, the dynamic deformation behavior of magnetic pressure parallel seam welding of aluminum sheets. Welding principle The welding principle is shown in Fig. 1. Magnetic pressure parallel seam welding uses electromagnetic force to accelerate one metal sheet (flyer plate) against another stationary metal Explosion Shock Waves and High Strain Rate Phenomena
磁压缝焊作为铝薄板的一种新型连接方法,受到了广泛的关注。磁压缝焊是一种以电磁力为加速机构的碰撞焊接工艺。电磁缝焊是在金属材料周围突然加入高密度磁通量,利用产生的电磁力使薄板在高速高压焊接中变形的方法。本文研究了平行铝缝焊接铝板的变形行为。采用有限元法对金属板的动态变形过程进行了数值分析。本分析所用样品假定为由平面应变四边形单元组成的铝制薄板(A1050-H24,宽度100mm,厚度1mm)。实验结果表明,该方法能较好地再现铝板间的碰撞速度。在初始碰撞点,铝板表面之间的碰撞点速度很高,但在焊接过程中,碰撞点速度不断下降。同时发现,间隙越小,碰撞点移动速度越快。铝的导电性和导热性比铁高,加热效率低,焊接困难。在以往的研究中,有关于磁压缝焊方法的报道[1]-[14]。磁压缝焊是一种类似爆炸焊接的碰撞焊接工艺,利用电磁力作为加速机制。磁压缝焊利用电磁力将某一金属板(飞片板)加速碰撞到另一固定金属板(母板)上。当来自电容器组的脉冲电流通过扁平的一匝线圈时,线圈中立即产生磁通。涡流是在线圈中的绝缘飞片中产生的。在磁压并联缝焊中,一匝线圈并联布置。沿线圈纵向部分飞片向母板凸起,飞片与母板发生碰撞焊接。高速碰撞时,试样焊接界面有金属射流喷出[7]。碰撞点速度和碰撞角由主电磁力和感应电磁力决定。如果接触发生在适当的碰撞点速度和碰撞角度之上,则在配合界面上实现真正的金属结合[15]。本文旨在探讨铝板磁压平行缝焊的动态变形行为。焊接原理焊接原理如图1所示。磁压平行缝焊利用电磁力加速一个金属片(飞片)对另一个静止金属爆炸冲击波和高应变率现象材料研究论坛LLC材料研究进展13 (2019)47-52 https://doi.org/10.21741/9781644900338-8 48片(母板)。当突然产生高磁场B并进入金属片时,涡流(电流密度i)穿过金属片。因此,式2的电磁力主要作用在飞片上,并被加速远离线圈,与母板发生快速碰撞[10]。涡流i,电磁力f和焦耳热Q给出如下。κ和B为铝板的电导率和磁通密度。当电磁成形装置的剩余电感较大时,大电流很难通过一匝线圈,因此磁压也变小,难以接合。由于多匝线圈线圈的电感比单匝线圈的电感高,因此可以增大通过线圈的电流,增大磁压。rot i =−κ∂B∂(1)
{"title":"Collision Behavior in Magnetic Pressure Parallel Seam Welding of Aluminum Sheets","authors":"A. Hatta, Y. Kajiro","doi":"10.21741/9781644900338-8","DOIUrl":"https://doi.org/10.21741/9781644900338-8","url":null,"abstract":"Magnetic pressure seam welding has attracted attention as a new joining method for aluminum thin plates. Magnetic pressure seam welding is a collision welding process, utilizing electromagnetic force as the acceleration mechanism. The electromagnetic seam welding is a method of abruptly adding a high density magnetic flux around a metal material and utilizing the generated electromagnetic force to deform the thin plate at high speed and pressure welding. This paper deal with the deformation behavior of parallel aluminum seam welded aluminum sheet. Numerical analysis of the dynamic deformation process of the metal plate is performed by the finite element method. The sample used for this analysis is assumed to be a thin plate made of aluminum (A1050-H24, width100mm, thickness 1mm) and composed of quadrilateral elements of plane strain. The experimental results show that the collision speed between the aluminum plates is sufficiently reproduced. The impact point velocity between the aluminum plate surfaces was very high at the initial collision point but decreased continuously during welding. It was also found that the smaller the gap is, the faster the collision point moving speed becomes. Introduction Aluminum has higher electrical conductivity and thermal conductivity than iron, so welding is difficult due to low heating efficiency. In previous studies, there is a report on the magnetic pressure seam welding method [1]-[14]. Magnetic pressure seam welding is a collision welding process similar to explosive welding and utilizes electromagnetic force as an acceleration mechanism. Magnetic pressure seam welding accelerates and collides a certain metal plate (flyer plate) to another stationary metal plate (parent plate) by using electromagnetic force. When an impulse current from a capacitor bank passes through a flat one-turn coil, a magnetic flux is instantaneously generated in the coil. The eddy currents are induced in insulated flyer plate in the coil. In magnetic pressure parallel seam welding, one-turn coils are arranged in parallel. A part of flyer plate along the longitudinal direction of the coil bulged toward a parent plate, then flyer plate collided and was welded to a parent plate. At the time of the high-speed collision, metal jets are emitted in the welding interface of the specimen [7]. The collision point velocity and collision angle are determined by the primary and induced electromagnetic force. True metallic bonding is achieved at the mating interface if contact takes place above an appropriate collision point velocity and collision angle [15]. The purpose of this paper is to discuss, the dynamic deformation behavior of magnetic pressure parallel seam welding of aluminum sheets. Welding principle The welding principle is shown in Fig. 1. Magnetic pressure parallel seam welding uses electromagnetic force to accelerate one metal sheet (flyer plate) against another stationary metal Explosion Shock Waves and High Strain Rate Phenomena ","PeriodicalId":415881,"journal":{"name":"Explosion Shock Waves and High Strain Rate Phenomena","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121267903","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}