This paper presents a procedure for identifying the free-free vibration data of a structure from the available vibration data of the same structure with boundary conditions. For a structure in a mechanical system, depending upon the dynamic formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the structure is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a structure supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for structures to be used in dynamic formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.
{"title":"Free-Free Vibration Extraction From Available Vibration Data","authors":"Thomas T. Yi","doi":"10.1115/imece2000-1255","DOIUrl":"https://doi.org/10.1115/imece2000-1255","url":null,"abstract":"\u0000 This paper presents a procedure for identifying the free-free vibration data of a structure from the available vibration data of the same structure with boundary conditions. For a structure in a mechanical system, depending upon the dynamic formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the structure is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a structure supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for structures to be used in dynamic formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126092458","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}
Harbor Branch Oceanographic Institution (HBOI) is using its spherical acrylic manned submersible for ocean exploration for last 3 decades. However, the development of tiny shear cracks at the interface areas of these submersibles following only few hundred dives require frequent, expensive repairs. To overcome this crack generation problem, a two-Phase research program is initiated at HBOI. In the Phase I of this study, a detailed nonlinear 3-D Finite Element Analysis (FEA) is performed at first to increase the understanding of the mechanical behavior at the interface of this submersible and then various analyses are carried out to develop a guidelines for redesigning the spherical acrylic submersible. Complete redesigning of the bottom of acrylic submersible is only presented here in details, as the discussion on the top of acrylic submersible is presented earlier. Based on the new design guidelines, in the Phase II of this study, a new spherical acrylic submersible is fabricated at HBOI. Brief discussion of the experimental results on the new submersible is also presented here. A significant reduction in peak stresses and a very small relative displacement at the gasket/acrylic interface which are believed to be two of the main causes for crack development at the interface areas clearly indicate a major improvement in the new design of the acrylic submersible, as they are also suggested by the extensive FEA results. This improvement in design is expected to extend the crack free cyclic fatigue life of the acrylic submersible at 3000 ft (914.4 m) ocean depth significantly.
{"title":"Redesign of Spherical Acrylic Submersible for Manned Operation to 3000 ft (914.4 m) Ocean Depth","authors":"P. S. Das","doi":"10.1115/imece2000-1265","DOIUrl":"https://doi.org/10.1115/imece2000-1265","url":null,"abstract":"\u0000 Harbor Branch Oceanographic Institution (HBOI) is using its spherical acrylic manned submersible for ocean exploration for last 3 decades. However, the development of tiny shear cracks at the interface areas of these submersibles following only few hundred dives require frequent, expensive repairs. To overcome this crack generation problem, a two-Phase research program is initiated at HBOI. In the Phase I of this study, a detailed nonlinear 3-D Finite Element Analysis (FEA) is performed at first to increase the understanding of the mechanical behavior at the interface of this submersible and then various analyses are carried out to develop a guidelines for redesigning the spherical acrylic submersible. Complete redesigning of the bottom of acrylic submersible is only presented here in details, as the discussion on the top of acrylic submersible is presented earlier.\u0000 Based on the new design guidelines, in the Phase II of this study, a new spherical acrylic submersible is fabricated at HBOI. Brief discussion of the experimental results on the new submersible is also presented here. A significant reduction in peak stresses and a very small relative displacement at the gasket/acrylic interface which are believed to be two of the main causes for crack development at the interface areas clearly indicate a major improvement in the new design of the acrylic submersible, as they are also suggested by the extensive FEA results. This improvement in design is expected to extend the crack free cyclic fatigue life of the acrylic submersible at 3000 ft (914.4 m) ocean depth significantly.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114571884","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}
A compound plate element is presented for modeling all layers of the damped structure into a single element. By associating deformations of the damping layer to those of base structure layer and constraining layer, the kinetic and potential energies of the damping layer as well as those of base and constraining layers can be derived. Then the element mass and stiffness matrices can be obtained for all layers as a whole. The newly derived element formulation results in significant simplification of constrained layer modeling and dramatic reduction of element density while maintaining the desired accuracy. The use of the element also allows direct and more accurate calculation of structural modal damping in modal analysis.
{"title":"Finite Element Modeling for Vibration Analysis of Constrained Layer Damping Treated Structures","authors":"Yanchu Xu, D. Chen","doi":"10.1115/imece2000-1254","DOIUrl":"https://doi.org/10.1115/imece2000-1254","url":null,"abstract":"\u0000 A compound plate element is presented for modeling all layers of the damped structure into a single element. By associating deformations of the damping layer to those of base structure layer and constraining layer, the kinetic and potential energies of the damping layer as well as those of base and constraining layers can be derived. Then the element mass and stiffness matrices can be obtained for all layers as a whole. The newly derived element formulation results in significant simplification of constrained layer modeling and dramatic reduction of element density while maintaining the desired accuracy. The use of the element also allows direct and more accurate calculation of structural modal damping in modal analysis.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129574004","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}
A simple (quadratic) mathematical model for predicting the deflection path of both non-tapered and continuously tapered cantilever beams loaded with a vertical end force is presented. It is based on the proposition that the path is a function of the ratio of the endpoints’ moments of inertia. The model is valid for both small and large (the tip makes a 70 degree angle with the horizontal) deflections. This was verified through physical testing, comparison to solution of the Bernoulli-Euler equation, and results obtained through nonlinear finite element analysis. Predicted endpoint deflections were found to be accurate within 1.8% of the actual deflection path for moment of inertia ratios varying from 1:1 to 1000:1.
{"title":"Predicting the Large Deflection Path of End-Loaded Tapered Cantilever Beams","authors":"M. Parkinson, G. Roach, L. Howell","doi":"10.1115/imece2000-1270","DOIUrl":"https://doi.org/10.1115/imece2000-1270","url":null,"abstract":"\u0000 A simple (quadratic) mathematical model for predicting the deflection path of both non-tapered and continuously tapered cantilever beams loaded with a vertical end force is presented. It is based on the proposition that the path is a function of the ratio of the endpoints’ moments of inertia. The model is valid for both small and large (the tip makes a 70 degree angle with the horizontal) deflections. This was verified through physical testing, comparison to solution of the Bernoulli-Euler equation, and results obtained through nonlinear finite element analysis. Predicted endpoint deflections were found to be accurate within 1.8% of the actual deflection path for moment of inertia ratios varying from 1:1 to 1000:1.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114137727","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}
Woven composites have good properties in mutually orthogonal directions, more balanced properties than unidirectional laminates and have better impact resistance. The use of these composites for primary structural applications in place of conventional laminated composites has been increased considerably in the recent years. They are being manufactured by using new processes such as Resin Infusion (VARIM) and Resin Transfer Molding (RTM). These new processes are low cost, affordable and suitable for high volume manufacturing environment. One of the popular plain woven composites is fabricated using S2-Glass and SC-15 resin system components by using Resin Infusion (VARIM) process. These woven composites are being evaluated for Integral Armor applications. These components are expected to be under fatigue loading. To assess the feasibility of this material manufactured through Resin Infusion (VARIM), it is very important to understand the fatigue behavior of these composite materials. The present study provides comparison of the performance evaluation of plain and twill woven composite material for Integral Armor applications. Tension-Compression (R = −1) fatigue experiments were performed. All the fatigue tests are performed at 1 Hz frequency. S-N diagram and stiffness degradation over the fatigue life of the specimens were obtained.
{"title":"Comparative Study of S2 Glass Plain and Twill Woven Composites Under Fatigue Loading","authors":"A. Kelkar, Sunil S. Shenoy","doi":"10.1115/imece2000-1257","DOIUrl":"https://doi.org/10.1115/imece2000-1257","url":null,"abstract":"\u0000 Woven composites have good properties in mutually orthogonal directions, more balanced properties than unidirectional laminates and have better impact resistance. The use of these composites for primary structural applications in place of conventional laminated composites has been increased considerably in the recent years. They are being manufactured by using new processes such as Resin Infusion (VARIM) and Resin Transfer Molding (RTM). These new processes are low cost, affordable and suitable for high volume manufacturing environment. One of the popular plain woven composites is fabricated using S2-Glass and SC-15 resin system components by using Resin Infusion (VARIM) process. These woven composites are being evaluated for Integral Armor applications. These components are expected to be under fatigue loading. To assess the feasibility of this material manufactured through Resin Infusion (VARIM), it is very important to understand the fatigue behavior of these composite materials. The present study provides comparison of the performance evaluation of plain and twill woven composite material for Integral Armor applications. Tension-Compression (R = −1) fatigue experiments were performed. All the fatigue tests are performed at 1 Hz frequency. S-N diagram and stiffness degradation over the fatigue life of the specimens were obtained.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125363553","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}
Y. Suh, Jong Sung Ahn, S. Choi, Hyun-ki Park, Y. J. Kim, Keeman Kim
To construct the CICC for the superconducting Tokamak fusion device, the 3-roll bending, that inherently has a difficulty to form the coil with accurate radius of curvature, is used for continuous winding. In order to obtain precise dimension, a trial-an-error operation is inevitable. To reduce the effort of tryout, a relation between travel of the bending roller and spring back displacement was obtained via virtual manufacturing. The radius of CICC after forming was expressed as a function of the bend-roll travel. Next, the variation of the CICC cross-section (reduction of the conduit cross-section) was investigated during the first turn and during conduit bending with largest curvature. With largest curvature, the cross-sectional area was not much reduced. Finally, the residual stress on the CICC before roll bending was measured in order to examine the influence of the original residual stress on the final deformation behavior. The principal stress and von Mises stress were measured at the surface of CICC using specially designed strain gauge. The measured values were considered in the virtual forming. The results indicate that the residual stresses generated during the fabrication of the CICC (before coiling) do not have much influence on the final stress state.
{"title":"Prediction for Post-Forming Spring Back of CICC in the Superconducting Tokamak Fusion Device via Virtual Manufacturing","authors":"Y. Suh, Jong Sung Ahn, S. Choi, Hyun-ki Park, Y. J. Kim, Keeman Kim","doi":"10.1115/imece2000-1263","DOIUrl":"https://doi.org/10.1115/imece2000-1263","url":null,"abstract":"\u0000 To construct the CICC for the superconducting Tokamak fusion device, the 3-roll bending, that inherently has a difficulty to form the coil with accurate radius of curvature, is used for continuous winding. In order to obtain precise dimension, a trial-an-error operation is inevitable. To reduce the effort of tryout, a relation between travel of the bending roller and spring back displacement was obtained via virtual manufacturing. The radius of CICC after forming was expressed as a function of the bend-roll travel. Next, the variation of the CICC cross-section (reduction of the conduit cross-section) was investigated during the first turn and during conduit bending with largest curvature. With largest curvature, the cross-sectional area was not much reduced. Finally, the residual stress on the CICC before roll bending was measured in order to examine the influence of the original residual stress on the final deformation behavior. The principal stress and von Mises stress were measured at the surface of CICC using specially designed strain gauge. The measured values were considered in the virtual forming. The results indicate that the residual stresses generated during the fabrication of the CICC (before coiling) do not have much influence on the final stress state.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131313628","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}
Solder joints are extensively used in electronic packaging. They provide critical electrical and mechanical connections. Single edge notched sandwich specimens, which were made of two blocks of brass joined with a 63Sn-37Pb solder layer, were prepared for fatigue and fracture study of the joint under mixed mode loading. Mode I and mixed mode I/II fracture toughness, fatigue crack thresholds, and fatigue crack growth rates (FCGR) were measured at room temperature using a four point bending test setup. It was found that the fracture toughness of the joint increased and FCGR decreased upon the introduction of mode II component. The interface fracture toughness was higher than that of reported for pure solder. The data of FCGR correlated well with the power law relation of da / dN = C* (ΔG)m. It was also observed that both fracture toughness and FCGR were a function of thickness of solder layer. When the solder layer thickness increased from 0.1mm to 1.0mm, the fracture toughness decreased substantially and FCGR increased slightly. For mode I loading, fatigue crack propagated inside the solder layer. However, for mixed mode loading, once a crack initiated, it changed its direction toward the interface and then propagated along the interface. These observations were related to local mode I and mode II stress fields. Fracture surface showed sign of rubbing under mixed mode loading with elongated cavities at the crack tip. However, under mode I loading, fracture surface was covered with equi-ax voids.
{"title":"Mixed Mode I/II Fracture and Fatigue Crack Growth Along 63Sn-37Pb Solder/Brass Interface","authors":"H. Nayeb-Hashemi, P. Yang","doi":"10.1115/imece2000-1258","DOIUrl":"https://doi.org/10.1115/imece2000-1258","url":null,"abstract":"\u0000 Solder joints are extensively used in electronic packaging. They provide critical electrical and mechanical connections. Single edge notched sandwich specimens, which were made of two blocks of brass joined with a 63Sn-37Pb solder layer, were prepared for fatigue and fracture study of the joint under mixed mode loading. Mode I and mixed mode I/II fracture toughness, fatigue crack thresholds, and fatigue crack growth rates (FCGR) were measured at room temperature using a four point bending test setup.\u0000 It was found that the fracture toughness of the joint increased and FCGR decreased upon the introduction of mode II component. The interface fracture toughness was higher than that of reported for pure solder. The data of FCGR correlated well with the power law relation of da / dN = C* (ΔG)m. It was also observed that both fracture toughness and FCGR were a function of thickness of solder layer. When the solder layer thickness increased from 0.1mm to 1.0mm, the fracture toughness decreased substantially and FCGR increased slightly.\u0000 For mode I loading, fatigue crack propagated inside the solder layer. However, for mixed mode loading, once a crack initiated, it changed its direction toward the interface and then propagated along the interface. These observations were related to local mode I and mode II stress fields. Fracture surface showed sign of rubbing under mixed mode loading with elongated cavities at the crack tip. However, under mode I loading, fracture surface was covered with equi-ax voids.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127258068","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}
The consequence of thermal treatment on the precipitation response of intermetallic precipitates in the microstructure microstructure and subsequent mechanical properties of an Al-2.6wt.%Li-0.09wt.%Zr alloy was studied. The alloy was solution heat treated and artificially aged for a series of aging times and temperatures at various precipitation hardening conditions. The underaged, peak-aged and overaged microstructures of the alloy were analyzed. Quantitative particle size measurements were performed to determine the size, distribution, morphology and coarsening rate for both δ′(Al3Li) and δ′(Al3Li)/Al3Zr precipitates. The average particle size, distribution, spacing and volume fraction of the intermetallic precipitates were related to the heat treating process. For all of the aging times studied, the δ′(Al3Li)/Al3Zr particles were much larger in size than the δ′(Al3Li) and Al3Zr-free particles. The particle coarsening rate, determined from the Lifshitz, Slyozov and Wagner coarsening rate theory, was more accelerated for the δ′(Al3Li)/Al3Zr particles than for the δ′(Al3Li) precipitates. The presence of the Al3Zr phase was found to accelerate the aging kinetics of the alloy. Therefore, a small amount of zirconium in the alloy resulted in a faster particle coarsening rate of the overall combined particle size distribution and thus led to more rapid precipitation aging response.
{"title":"The Effect of Aging on the Microstructure and Precipitation Response of an Aluminum-Lithium Alloy","authors":"J. Fragomeni","doi":"10.1115/imece2000-1260","DOIUrl":"https://doi.org/10.1115/imece2000-1260","url":null,"abstract":"\u0000 The consequence of thermal treatment on the precipitation response of intermetallic precipitates in the microstructure microstructure and subsequent mechanical properties of an Al-2.6wt.%Li-0.09wt.%Zr alloy was studied. The alloy was solution heat treated and artificially aged for a series of aging times and temperatures at various precipitation hardening conditions. The underaged, peak-aged and overaged microstructures of the alloy were analyzed. Quantitative particle size measurements were performed to determine the size, distribution, morphology and coarsening rate for both δ′(Al3Li) and δ′(Al3Li)/Al3Zr precipitates. The average particle size, distribution, spacing and volume fraction of the intermetallic precipitates were related to the heat treating process. For all of the aging times studied, the δ′(Al3Li)/Al3Zr particles were much larger in size than the δ′(Al3Li) and Al3Zr-free particles. The particle coarsening rate, determined from the Lifshitz, Slyozov and Wagner coarsening rate theory, was more accelerated for the δ′(Al3Li)/Al3Zr particles than for the δ′(Al3Li) precipitates. The presence of the Al3Zr phase was found to accelerate the aging kinetics of the alloy. Therefore, a small amount of zirconium in the alloy resulted in a faster particle coarsening rate of the overall combined particle size distribution and thus led to more rapid precipitation aging response.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"24 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125892945","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 general, precision machine tools consist of a number of structural components, usually castings machined and bolted together to very tight and precise tolerances. Machine bolts are used to prevent the contact surfaces from separating or sliding relative to each other. The issues critical in the design of these precision bolted joints include tensile, compressive, and lateral stiffness, and stability of the joint under different types of load. In machine tool design, the shape and tightening force in these joints are usually evaluated based on two counteracting requirements: (1) maintain sufficient stiffness provided by the joint at the cutting (load) point, and (2) allow the joint to slip (breakaway) in the event of a machine crash; in this case, the bolted joint works as a fuse preventing damage and, thus, protect critical/expensive components in the machine and/or avoid extensive repairs. Field data from machines running production have shown that satisfaction of the two criteria, presented above, using conventional methods of bolted joint design does not always assure that the stability requirements are met. This data shows that in the range of loads that do not exceed the maximum force allowed in the machine, there might occur permanent lateral displacements in the joint. These displacements accumulate during normal operations under repeated loads and the machine looses alignment without obvious instantaneous slippage in the joint. This paper discusses an approach that gives a qualitative and numerical evaluation of the joint shape, position of the bolts, tightening force, and load that it can withstand without compromising the joint integrity while still providing an effective breakaway for the protection of critical components.
{"title":"Optimization of Mission Critical Joints in Bolted Machine Tool Structures","authors":"E. Kushnir, M. R. Patel, T. Sheehan","doi":"10.1115/imece2000-1268","DOIUrl":"https://doi.org/10.1115/imece2000-1268","url":null,"abstract":"\u0000 In general, precision machine tools consist of a number of structural components, usually castings machined and bolted together to very tight and precise tolerances. Machine bolts are used to prevent the contact surfaces from separating or sliding relative to each other. The issues critical in the design of these precision bolted joints include tensile, compressive, and lateral stiffness, and stability of the joint under different types of load.\u0000 In machine tool design, the shape and tightening force in these joints are usually evaluated based on two counteracting requirements: (1) maintain sufficient stiffness provided by the joint at the cutting (load) point, and (2) allow the joint to slip (breakaway) in the event of a machine crash; in this case, the bolted joint works as a fuse preventing damage and, thus, protect critical/expensive components in the machine and/or avoid extensive repairs.\u0000 Field data from machines running production have shown that satisfaction of the two criteria, presented above, using conventional methods of bolted joint design does not always assure that the stability requirements are met. This data shows that in the range of loads that do not exceed the maximum force allowed in the machine, there might occur permanent lateral displacements in the joint. These displacements accumulate during normal operations under repeated loads and the machine looses alignment without obvious instantaneous slippage in the joint.\u0000 This paper discusses an approach that gives a qualitative and numerical evaluation of the joint shape, position of the bolts, tightening force, and load that it can withstand without compromising the joint integrity while still providing an effective breakaway for the protection of critical components.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"122 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114168654","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}
Techniques in computational fracture mechanics were employed to optimize the performance of a fracture specimen for use in crack growth studies in a constant K environment. The finite element method was used to model the specimen. In the numerical calculations, the mode I stress intensity factors were obtained using a domain integral approach. The specimen was optimized by systematically changing its geometry and performing finite element calculations in an iterative fashion. The procedure was carried out until a variation in the mode I stress intensity factor of less than three percent within the desired range of crack propagation was achieved.
{"title":"An Optimized Specimen for Crack Growth Studies in a Constant K Environment","authors":"R. Cammino, M. Gosz, S. Mostovoy","doi":"10.1115/imece2000-1250","DOIUrl":"https://doi.org/10.1115/imece2000-1250","url":null,"abstract":"\u0000 Techniques in computational fracture mechanics were employed to optimize the performance of a fracture specimen for use in crack growth studies in a constant K environment. The finite element method was used to model the specimen. In the numerical calculations, the mode I stress intensity factors were obtained using a domain integral approach. The specimen was optimized by systematically changing its geometry and performing finite element calculations in an iterative fashion. The procedure was carried out until a variation in the mode I stress intensity factor of less than three percent within the desired range of crack propagation was achieved.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132539289","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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