bluuebunny/crossref_metadata_2025 huggingface dataset:
Global Buckling and Initial Post-Buckling Behavior of Sandwich Beams Including Transverse Shear
Authors: Kardomateas George A.
Published: November 2021

An asymptotic solution is presented for the buckling and initial postbuckling behavior of sandwich beams. The effect of transverse shear is included and the shear correction is calculated from energy equivalency. The asymptotic procedure is based on the nonlinear beam equation (with transverse shear included) and closed form solutions are derived for the critical loas and for the load and mid-point delamination deflection and axial shortening versus applied compressive load during the initial postbuckling phase. Illustrative results are presented for a few typical sandwich construction configurations, in particular with regard to the effect of face sheet and core material system.
Target Stress Prediction for Durability Analysis
Authors: Zhang Zongfen
Published: November 2021

This paper present a methodology to predict target stress under a unit load for a given load schedule, material and geometry analytically. This approach improves the conventional way of doing fatigue and life prediction. This method can be used to any parts/subsystems, which have durability issue. The advantages of knowing the target stress analytically include cost saving in term of hardware reduction and development time saving because the further validation time of design can be shorten. As an example, a decklid global latch design is discussed.
A Bodner Type of Material Model for the Description of Foam Properties
Authors: Song Yuzhao , Chen Ziqi
Published: November 2021

A unified constitutive equation has been used to represent Foam material. It can describe the large compression strain, compression strain rate, tension strain and the bottom out behavior of various foams. The material has been incorporated into LS-DYNA, an explicit finite element code widely used in the automobile industry. An example is given to show an application of the material model in a low speed impact finite element analysis.
Core Failure Modes in Composite Sandwich Beams
Authors: Daniel Isaac M. , Gdoutos Emmanuel E. , Abot Jandro L. , Wang Kuang-An
Published: November 2021

Core failure modes were studied in composite sandwich beams under three-point bending and in cantilever beams under end loading. The beams consisted of unidirectional carbon/epoxy face sheets and a variety of core materials, including aluminum honeycomb, PVC closed-cell foams, polyurethane foam and balsa wood. The constituent materials were fully characterized and in the case of the core materials, failure envelopes were developed for biaxial states of stress. Deformation and failure mechanisms were studied experimentally by means of moiré gratings and birefringent coatings. Results were obtained for stress (strain) distributions in the linear and nonlinear/plastic range of the core, critical failure loads and their dependence on geometrical dimensions, material parameters and loading conditions.
Damage Initiation and Evolution in Woven Composites
Authors: Tang Xiaodong , Whitcomb John D.
Published: November 2021

The damage initiation and evolution mechanisms in plain and satin weave composites were studied using three-dimensional finite element analysis. The tow paths of the weave were selected such that the wavy region of the tows were identical in both weaves. The damage initiation and evolution behaviors in these comparable wavy regions were compared and discussed in terms of stress components that initiate damage, the overall stress/strain relationship and the accumulation of the damaged volume in the warp tow, fill tow and matrix pockets. The results showed significant similarities in many aspects of the damage behaviors such as damage modes, stiffness loss and damage accumulation processes.
Fiber Pullout Characteristics Under Dynamic Loading Conditions
Authors: Sridhar N. , Yang Q. D. , Cox B. N.
Published: November 2021

Inertial effects in the mechanism of fiber pullout during dynamic propagation of a bridged crack are critically examined. By reposing simple shear lag models of pullout as problems of dynamic wave propagation, the effect of frictional coupling between the fiber and the matrix is accounted for in a fairly straightforward way. The frictional sliding between the fiber and the matrix is described by a constant interfacial friction stress, the sign of which depends on the relative particle velocity of the fiber and the matrix. Analytical solutions are derived when the load or bridging traction on the fiber in the crack plane increases linearly in time. The results show that when the wave speed of the matrix exceeds a critical value, the frictional fiber pullout behavior transitions from a state of pure slip to a state where part of the sliding zone slips and the remaining sticks. When stick occurs, the fiber and the matrix within the stick zone slide past each other with an interfacial shear stress less than the shear stress required for slipping. Regions of slip and stick propagate and increase with time and influence the time-dependent relationship between the crack opening displacement and the bridging tractions.
Bending Failure Behavior of Recycled Aluminum Reinforced Composites
Authors: June Brian M. , Pidaparti Ramana M. , El-Mounayri Hazim
Published: November 2021

In order to effectively use the recycled aluminum cans, many applications of aluminum are being explored. One of the most obvious applications is to reinforce with wood or others, to form sandwich composites. The goal of the proposed work is to conduct the research to develop constructional products, which would permit reuse of aluminum cans instead of destroying the structure by melting or trashing. With that goal in mind, our specific objective of this study is to evaluate the stiffness and failure behavior of recycled aluminum reinforced composites under three-point bending for use in composite industries. Composite specimens containing the end sections of the can sandwiched between top and bottom layers of wood are investigated. The results of bending stiffness and failure behavior of sandwich composite panels obtained from the three-point bending tests are presented and discussed.
Design Study of Composite Sandwich Truck Tank Using a High-Order Sandwich Theory Approach
Authors: Thomsen Ole T. , Vinson Jack R.
Published: November 2021

The paper presents a preliminary design study on the structural response of a boxy composite sandwich truck tank subjected to hydraulic head loading. The design study is approximate in that it considers a 2-D cross section of the composite sandwich truck tank. The design study is performed using a high-order sandwich theory formulation in which the elastic responses of the face laminates are accounted for individually, and in which the transverse flexibility of the sandwich core is included. Thus the model allows the sandwich panel thickness of the truck tank to change during deformation, and the model accounts for the existence of transverse normal stresses in the core material in the sandwich panel sections. The paper includes a presentation of the high-order formulation for the curved sandwich panel parts of the composite sandwich truck tank sections, as well as a brief description of the numerical solution of the complete set of system equations with corresponding boundary conditions. The paper is concluded with a numerical study, showing the characteristic features of the elastic response of a composite sandwich truck tank section subjected to hydraulic head loading.
Dynamic Response of Sandwich Anisotropic Flat Panels to Explosive Pressure Pulses
Authors: Hause Terry , Librescu Liviu
Published: November 2021

This paper addresses the problem of the dynamic response in bending of flat sandwich panels exposed to time-dependent external pulses. The study is carried out in the context of an advanced model of sandwich structures that is characterized by anisotropic laminated face sheets and an orthotropic core layer. A detailed analysis of the influence of a large number of parameters associated with the particular type of pressure pulses, panel geometry, fiber orientation in the face sheets and, presence of tensile uni/biaxial edge loads is accomplished, and pertinent conclusions are outlined.
Free Vibration of High-Order Curved Sandwich Beams
Authors: Frostig Yeoshua , Bozhevolnaya Elena
Published: November 2021

A high-order model for free vibrations of singly curved sandwich beams is presented. The model takes into account the transverse flexibility of the sandwich core while the faces of the sandwich are treated as thin beams. Linear equations of motion as well as the natural boundary conditions are derived. It is shown for the curved sandwich beams, that there exist four eigen modes. A numerical analysis of free vibration of the simply supported beams is carried out. Effects of design parameters of the sandwich constituents on the eigen modes and their appropriate frequencies are investigated.
Suddenly Arrested Intersonic Shear Crack
Authors: Huang Y. , Gao H.
Published: November 2021

We study a mode II crack suddenly stopping after propagating intersonically for a short time. The solution is obtained by superposing the fundamental solution and the auxiliary problem of a static crack emitting dynamic dislocations such that the relative crack face displacement in the fundamental solution is negated ahead of where the crack tip has stopped. We find that, after the crack stops moving, the stress intensity factor rapidly rises to a finite value and then starts to change gradually toward the equilibrium value for a static crack. A most interesting feature is that the static value of stress intensity is reached neither instantaneously like a suddenly stopping subsonic crack nor asymptotically like a suddenly stopping edge dislocation. Rather, the dynamic stress intensity factor changes continuously as the shear and Rayleigh waves catch up with the stopped crack tip from behind, approaches negative infinity when the Rayleigh wave arrives, and then suddenly assumes the equilibrium static value when all the waves have passed by. This study is an important step toward the study of intersonic crack propagation with arbitrary, non-uniform velocities.
High Strain Rate Response of PVC Foams
Authors: Thomas Tonnia , Mahfuz Hassan , Carlsson Leif A. , Kanny Krishnan , Jeelani Shaik
Published: November 2021

In this study, cross-linked poly-vinylchloride (PVC) closed-cell foams were examined under high strain rate compression loading using a servohydraulic testing machine and a modified Split Hopkinson Pressure Bar (SHPB) apparatus with a steel incident bar and a polycarbonate transmitter bar for strain rates up to 2000 s−1. Three foam densities were examined, viz. 75, 130, and 260 kg/m3.

The stress and strain-time history and stress-strain behavior were evaluated. An increase of stress and strain was observed for all categories of foam as strain rate increased. A post impact study was also performed to evaluate the failure modes of the foam cores. A densification band of collapsed cells was the major mode of failure.
Size Effect in Fracture of Sandwich Structure Components: Foam and Laminate
Authors: Bažant Zdeněk P. , Zhou Yong , Novák Drahomír , Daniel Isaac M.
Published: November 2021

In the design of sandwich plates and shells for very large structures, such as ships in the range of 100 m length, it is very important to take the size effect on the nominal strength into account, and do so in a realistic, physically justified, manner. Before the size effect is addressed for a sandwich structure, it must be understood for its components — the foam core and the laminate skins. In the current practice, the size effects are automatically attributed to the randomness of material strength, as described by the Weibull theory. The purpose of this paper is to show that in both the foam and the laminate there are deterministic size effects, which are generally more pronounced. They are caused by stress redistribution and energy release due to the growth of large fractures or large cracking zones prior to attaining the maximum load. This deterministic size effect is verified and calibrated by new tests of notched specimens of rigid close-cell vinyl foam. A combined deterministic-probabilistic theory of size effect of the laminates is proposed and verified by extensive test data.
Derived Interaction Parameters for the TSAI-WU Tensor Polynomial Theory of Strength for Composite Materials
Authors: DeTeresa Steven J. , Larsen Gregory J.
Published: November 2021

It is shown that the two interactive strength parameters in the Tsai-Wu tensor polynomial strength criterion for fiber composites can be derived in terms of the uniaxial or non-interacting strength parameters if the composite does not fail under practical levels of hydrostatic pressure or equal transverse compression. Thus the required number of parameters is reduced from seven to five and all five of the remaining strength terms are easily determined using standard test methods. The derived interactive parameters fall within the stability limits of the theory, yet they lead to open failure surfaces in the compressive stress quadrant. The assumptions used to derive the interactive parameters were supported by measurements for the effect of hydrostatic pressure and unequal transverse compression on the behavior of a typical carbon fiber composite.
Evolution of Interfacial Decohesion in Particulate Composites
Authors: Dvorak George J. , Zhang Jian
Published: November 2021

Evolution of distributed damage in heterogeneous solids is modeled using the Transformation Field Analysis method [Proc. R. Soc. Lond. A (1992) 437, 311–327] and selected models of interface debonding in fibrous or particulate composites, as described in detail in the forthcoming paper [J. Mech. Phys. Solids Boehler Memorial Volume, 2001]. In this approach, stress changes caused by local debonding under increasing overall loads are represented by residual stresses generated by damage-equivalent eigenstrains that act together with the applied mechanical loading program and physically based local transformation strains on an undamaged elastic aggregate. Damage rates are derived from a prescribed probability distribution of interface strength and local energy released by debonding. Numerical simulations of damage evolution in a glass/elastomer composite indicate which of these two conditions controls the process at different reinforcement densities and overall stress states. In general, the energy released by a single particle at given overall stress decreases with increasing reinforcement density, and in proportion to particle size. Therefore, dense reinforcement by smaller-diameter particles or fibers should enhance damage resistance of composite systems.
The High Velocity Impact Response of Novel Fiber Metal Laminates
Authors: Cantwell Wesley J. , Wade Graham , Guillen J. Fernando , Reyes-Villanueva German , Jones Norman , Compston Paul
Published: November 2021

The impact resistance of a range of novel fiber metal laminates based on polypropylene, polyamide and polyetherimide matrices has been investigated. Initial attention focused on optimizing the interface between the composite and aluminum alloy constituents. Here, it was shown that composite-metal adhesion was excellent in all systems examined. In addition, tests at crosshead displacement rates up to 3 m/s indicated that the interfacial fracture energies remained high under dynamic loading conditions.

High velocity impact tests on a series of 3/2 laminates (3 layers of aluminum/2 layers of composite) highlighted the outstanding impact resistance of a number of these systems. The glass fiber reinforced polypropylene system offered a particularly high impact resistance exhibiting a perforation energy of approximately 160 Joules. Here, failure mechanisms such as extensive plastic drawing in the aluminum layers and fiber fracture in the composite plies were found to contribute to the excellent energy-absorbing characteristics of these systems.
Dynamic Mechanical Properties of Fiber-Metal Laminates
Authors: Liu Jianjun , Liaw Benjamin , Pamwar Manish
Published: November 2021

Fiber-metal laminated cantilever beams, made of glass-fiber reinforced GLARE and aramid-fiber reinforced ARALL laminates interlaced with aluminum layers, were first excited by a shaker at various frequencies surrounding resonances. Dynamic Young’s moduli and damping ratios were then evaluated using both free-vibration (resonance) and forced-vibration (non-resonance) schemes. Results from both schemes are in good agreement. Compared to aluminum alloys, the dynamic Young’s moduli of fiber-metal laminates are relatively lower. For all types of fiber-metal laminates tested in this study, their values are almost constant within an excitation frequency range up to 5,000 Hz whereas the damping ratios oscillate within a narrow range of 0 to 0.02. The obtained dynamic moduli are in excellent agreement with their static counterparts. Better results were obtained when using a strain gage near the clamped end, as compared to a piezoelectric accelerometer at the tip.
Crashing Behavior of Braided Composites
Authors: Hamada Hiroyuki
Published: November 2021

FRP exhibits not only the excellent strength to weight than conventional metallic materials, but also high energy absorption properties. Therefore FRP would be applied to structural components for various vehicles recently. Particularly, braided composites are expected to utilize for safety components, because they show the fracture mode called progressive crushing, which proceeds under constant load. Energy absorption with progressive crushing was generated by combination of fiber fracture, delamination, crack, etc. In this paper, the crushing properties, especially fracture mechanisms of FRP rods were investigated. To discuss the fracture morphology, microscopic observations were examined.
Studies on Headform Impact Design
Authors: Deb Anindya
Published: November 2021

HIC(d) (Head Injury Criterion, dummy) is defined as a kinematic relationship involving resultant translational deceleration at the CG (center of gravity) of a biofidelic headform and duration of contact. As deceleration response of a headform is in general a function of the energy-absorbing and geometrical properties of an obstructing structure (for a given impact speed), HIC(d) can be expressed, at least symbolically, as a function of those properties. The current paper uses a simplified mathematical model to capture the worst case of headform impact as considered in the FMVSS 201 regulation for upper interior head impact. The obstructing structural countermeasure in the path of a colliding headform is assumed to possess idealized elastoplastic although physically relevant behavior under loading. During the process of designing for headform impact safety compliance, which often turns out to be a trial-and-error process, it is sometimes difficult to see the correspondence between HIC(d) and the relative effectiveness of design iterations in terms of energy-absorption. Thus, relationship between HIC(d) and energy absorbed by such structural countermeasures is investigated. Based on results obtained from the current model and a new approach, an explicit relationship is derived between HIC(d) and the characteristic properties of an energy-absorbing countermeasure that can be used as a design aid.
Frontal Impact Test and Analysis on an Aluminum Front-End Structure
Authors: Caliskan Ari G. , Koganti Rama
Published: November 2021

A frontal impact test was performed on a front-end module consisting of 6xxx series aluminum extrusions, and some 5xxx series aluminum stampings as reinforcements. The front end structure consists mainly of a bumper, cross member, radiator support, front and backup lower rails, upper rails, and shock tower support. In addition to the main structure, a subframe containing the engine was also attached to the back-up rails. The front-end module was mounted on a sled at the upper and lower A-pillar points as well as at the back-up rail. In addition to measuring the barrier forces, load cells were located behind the main structural members to determine load transfer. The results of the tests showed progressive folding of the crush rails, and adequate absorption of the impact energy. To aid in the design, a CAE model of the front-end was created to determine the crash behavior of the structure during frontal impact. The final model, which took into account, the material properties of the weld joints showed good agreement with test results.
Global Characterization of Failure Modes Under Impact Loading in Structural Components Made of Low Ductility Materials
Authors: Wu Shen Rong , Chen Xiaoming , Hu Weiran
Published: November 2021

This study reviews the impact failure modes of structural components made of materials with low ductility such as aluminum and magnesium. Tensile failure is observed at large stretch area or on the tension side of large bending deformation. Material breakage due to shear may also occur. There are several approaches to simulate the material failure process in explicit finite element software used for crashworthiness analysis. Evaluation of the effective applications of these material models is presented with a finite element simulation of bi-axial loading tests. The forming limit diagram is used to evaluate various failure criteria. Component crash simulations are presented to demonstrate the applications of failure criteria.
Evaluation of Rear Impact Seat System Performance Using a Combined Load Neck Injury Criteria and Hybrid III Surrogates
Authors: Saczalski Kenneth J. , Burton Joseph Lawson , Lewis Paul R. , Saczalski Todd K. , Baray Peter E.
Published: November 2021

Vehicle to vehicle rear impact crash tests and sled buck tests were run to evaluate seat system performance related to Hybrid III surrogate response and comparison with NHTSA proposed combined load injury assessment values, as well as standard injury criteria. The crash and sled buck test impact conditions were modeled after actual case study incidents where changes in the rear impacted vehicle speeds ranged from about 25 to 50 kph. With the exception of one baseline vehicle-to-vehicle rear impact test, the dynamic tests provided side-by-side comparisons, and test-to-test evaluations, of surrogate response in conventional yielding front seats versus much stronger seat systems such as the belt integrated seat designs. Head, neck and chest injury criteria were used in the evaluations, including both the proposed NHTSA combined load neck criteria and SAE J 885 injury values. The surrogate response injury levels for the conventional yielding seats correlated well with the actual case study injury results. The seat comparison response generally indicated much reduced head and neck injury potential to surrogates seated in the stronger seat designs. The dynamic tests also demonstrate the importance of testing within the full vehicle interior structure to insure that floor strength is compatible with seat strength, so as to attain optimum occupant protection in stronger seat designs, and to assess injury risk to occupants in yielding or collapsing seat designs, as well as rear seated occupants, such as children. The tests indicate that quasi-static seat strength measurements made with more realistic “torso body block” load devices can provide reasonable estimates on the ultimate failure modes and dynamic load capabilities of the seat systems if the seat systems are properly mounted to the vehicle. Quasi-static seat strength results are presented for a variety of conventional collapsing seat designs and stronger seat systems like the belt integrated designs. One sled buck test was run with a rear-seated child surrogate to demonstrate the hazard of front seat collapse into the rear seat occupant area. The results of these tests further demonstrate the need for dynamic testing to assess total seat system performance and full occupant protection in rear impacts.
The Development and Validation of a Finite Element Human Thorax Model for Automotive Impact Injury Studies
Authors: Chang Fred
Published: November 2021

Computational simulations are becoming more important in automotive safety engineering. To simulate the occupants during the crash environment, dummies are currently used to represent the occupants. However, current dummies and dummy models lack the detailed information to predict the occupant injuries during a crash. And for the human thorax models, simplified geometry and non strain-rate material properties were used for the rib cage with no ability to simulate the rib fractures often seen in an automotive crash. Therefore, a detailed finite element human thorax model with proper material properties and the capability to simulate the rib fractures is needed to better understand the thoracic injuries under frontal and side impacts.

The current thorax model, based on a previous skeleton model with heart and lung by Deng et al. [1]. used digital surface images to construct the three-dimensional finite element representation of the spine, rib cage, arms, surface muscles, heart, lungs, and major blood vessels. Strain-rate-dependent properties were utilized for the rib cage. With the rib fracture prediction, the model showed good correlation with the test results.
Extended Occupant Safety Through Virtual Testing: Objectives of the European Project VITES
Authors: van Hoof Jack , Happee Riender , Puppini Roberto , Baldauf Hans , Oakley Charles
Published: November 2021

Increasingly stringent international passenger safety norms and the need to reduce vehicle body weight for environmental and protection requirements demand efficient and innovative design methods. Computer simulation, or virtual testing, allows an integrated evaluation of these aspects in the early design stages and thereby reduces costs for prototyping and reduces time-to-market. This paper deals with the application of virtual testing in vehicle passive safety design to:

(1) reduce injury numbers by enhancing passive safety for a wide range of conditions, and

(2) reduce the duration and costs of the vehicle design by improving the efficiency of the design process.

A validated virtual test procedure will be developed to extend the range of protection beyond current regulations to real life crash conditions. This will be achieved by 1) developing procedures and guidelines to standardise numerical models and simulations; 2) accounting for the experimentally observed scatter in simulations by stochastic modelling; and 3) identify gaps in current regulations where occupants are not optimally protected. All steps needed for acceptance of this virtual test procedure in regulations or in a consumer test method will be taken into account.
The Possible Role of Fluid/Solid Interactions in Minor Cervical Spine Injuries
Authors: Niederer Peter F. , Schmitt Kai-Uwe , Muser Markus H. , Walz Felix H.
Published: November 2021

Minor soft tissue injuries of the cervical spine pose increasing problems in public health. Such injuries are conveyed particularly often in rear-end automobile collisions at low impact speeds and it has been established that they may be associated with long-term impairment Among the hypotheses put forward in order to explain the occurrence of potentially harmful neck injuries at loading levels whose severity is generally considered well below tolerance limits which hitherto have assumed to be valid, interactions between fluid and solid structures have been postulated as injury mechanism. As the solid structures of the human body, i.e., skeleton, muscles, etc., are being accelerated and deformed through the action of impact forces, the fluids contained therein (blood, cerebrospinal fluid, interstitial fluids) are gradually dragged along or displaced because of viscosity or pressure gradients which are built up in the deforming solids. Ensuing relative motions and changes of fluid volumes cause viscous shear stresses and pressure peaks which may have an adverse influence, e.g., on cellular membranes. This hypothesis is supported by a number of experimental findings.

In this communication, mathematical modeling approaches are presented which are aimed at a quantification of fluid/solid interactions under loading conditions which approximate the impact situations of interest here. For this purpose, idealized fluid and solid systems are first considered which are exposed to a constant acceleration. The geometries are chosen such that analytic solutions can be obtained. Second, a detailed neck model is presented which includes vertebrae, discs, muscles, tendons as well as a representative fluid space (plexus venosus). The models are subjected to boundary conditions which correspond to typical low-speed rear-end impacts. It is found, that the level of shear stresses caused by fluids and acting on surfaces in fluid-filled bodies depends essentially on the size of the fluid spaces under consideration. Accelerations thereby exhibit a stronger influence than the duration during which they act. It cannot be excluded that critical levels are reached even in a low speed impact scenario. Calculated pressure peaks, in turn, remain within physiological limits.
Frontal Offset Crash: Smart Structure Solution
Authors: Jawad Saad A. , Baccouche Mohamed Ridha
Published: November 2021

The majority of real world frontal collisions involve partial overlap of the vehicle front. Excessive, intrusion is usually generated on the impacted side subjecting occupants to higher contact injury risk compared with full frontal collision. The problem encountered by the front end design engineer is to address conflicting requirements of keeping the G-level in the full frontal crash within its permitted values, and minimizing intrusions in offset crash. Traditional solutions to this problem focus on the use of three forked and cross members to ensure continuity of the load path into the passenger compartment. The ideal structure for offset crash is to stiffen the impacted side of the structure, and transfer part of the load to the non-impacted side to even out the load on both sides. Smart hydraulic structure is proposed to meet these ideal requirements. Sample hydraulic “Smart Structures” were designed and tested for feasibility of crash under high-pressure and high-speed impact conditions.

This research is attempting to find a solution to the design trade off faced by the designer for offset crash. A novel system of “Smart Structures” is introduced to support the function of the existing passive structure. The proposed “Smart Structures” consist of two independently controlled hydraulic cylinders integrated with the front-end rails.

A ten-degrees of freedom, two-dimensional spring-mass-damper simulation model has been developed to study the dynamics of crash between two vehicles in head-on collisions. The model inputs mass, speed of both colliding vehicles, overlap ratio and deformation characteristics of both passive and “smart” structures. The model assumes that the two colliding structures geometrically interact with each other. Full simulations of various scenarios of offset crashes were investigated using “Smart Structures” integrated with the front rail members.

Deployable “Smart Structures” have not been considered in this paper as this scenario was covered in previous publication (9). “Smart Structures” proved superior to the traditional passive structures by absorbing more energy for the same crush zone distance, stiffening the impacted side and stiffening the structure at high-speed impacts. The results are reduced intrusion for offset crashes while maintaining the permitted G-level in both full and offset crashes.
Crush Characteristics of E-Glass Tubes in Off-Angle Impacts
Authors: Mahmood Hikmat F. , Loosle David G. , Moosa Adil G.
Published: November 2021

Off-angle impact behavior and specific energy absorption (SEA) of E-glass/polyurethane square tubes have been investigated under static and dynamic loading. Various fiber orientations, braided, CSM (Continuous Strand Mats), and RCM (Random Chopped Mats) lay-ups were used. Consistent test data suggested that dynamic off-angle crush forces are lower than the static ones. Dynamic maximum moments during a progressive crush are slightly higher than its static counterpart. Tubes constructed of CSM and RCM break-off when the maximum moment is reached whereas, tubes constructed of stitched/braided fiber fold upon reaching the maximum moment and remain intact. Specific energy absorption is reduced with the increase of impact angle due to combined loading effect. Certain lay-ups give more SEA than others. Ratios of average static to dynamic crush force are presented for different lay-ups and impact angles.
Development of Undergraduate Mechatronics Course in the School of Mechanical Engineering at Georgia Tech
Authors: Ume I. Charles , Kita Akio
Published: November 2021

As the field and applications of Mechatronics grow, engineering education must grow with it to meet the changing needs of students and industry. How to teach Mechatronics continues to be an open area for discussion. The subject is interdisciplinary and it is continuously changing. This presentation focuses on the structure and growth of the undergraduate Mechatronics courses in the Woodruff School of Mechanical Engineering at Georgia Tech. The goal is to provide students with a fun, hands-on, challenging, project based and collaborative learning approach to mechatronics education. An overview of the course and the laboratory experiences is presented. Student projects are included to highlight the topics tackled in the course.
Capstine Design Projects for Mechatronic Design in Mechanical Engineering Department
Authors: Erden Abdülkadir
Published: November 2021

The current paper describes the minor program in mechatronics engineering developed at the Middle East Technical University. The paper gives the main structure of the program with a discussion on the design of the new courses in mechatronics. Sample project topics are also given for the mechatronics design courses. Emphasis is placed on the design features of the mechatronics courses.
Failure Analysis and Redesign of a Pressure Powered Pump Mechanism
Authors: Brader John S. , Rocheleau David N.
Published: November 2021

This paper identifies the field failures of a Pressured Powered Pump (PPP) mechanism and presents the analysis and subsequent corrective action taken to prevent these failures. The Pressure Powered Pump is a mechanism that converts the liquid level within the body of the pump to the position and actuation of two valves on top of the pump. The two valves control motive pressure within the pump, and therefore, control the pumping action. Tracking in-use field data, it was seen that the pump fails at several locations, which, regardless of the location of the failure, can be attributed to an ill-designed crank-slide mechanism inside the pump. The purpose of the project, and thus the subject of this paper, is the analysis of these failures, the identification of the typical mode of failure, and the subsequent corrective action taken to prevent these types of failures.

The PPP project was executed at the University of South Carolina with support from the manufacturer of the pump. To identify and prevent failures of the pump, three phases were undertaken. First, a failure analysis of the existing mechanism and failed components was performed. Second, using the analysis information, a redesign of the pump was undertaken. And third, a new analysis was performed on the redesigned mechanism, which turned out to be a slider crank. The outcome of this work is a pump whose mechanism now operates under reduced forces and stresses; thus, results in a pump with a predictably longer lifecycle and far fewer failures.
Failure Analysis and Redesign of Some Import Motor-Driven Devices of Valve
Authors: Zhang Jiancheng , Zhou Entao , Zhou Shichang , Li Guodong , Liu Pengjie
Published: November 2021

Combining with the failure analysis of a class of import motor-driven devices of valve and the design of new kinds, several problems worth noticing in the design of motor-driven devices of valve have been discussed. These are the failure analysis and the redesign of changeover mechanism between manual operating and motor driving, the redesign of the setting way for valve opening, the reform of the measurement of transmission way for valve opening, and the selections of the parameters about velocity and force of the device. Based on these analyses, redesigned motor-driven devices of valve have been successfully applied in industry. The conclusions obtained have certain referential values to related research.
Failure Analysis of the Rear Axles in a Sports Utility Vehicle (SUV)
Authors: Rasty Jahan , Le Xiaobin
Published: November 2021

In a rollover accident, both rear axles of a Sports Utility Vehicle (SUV) were fractured adjacent to the wheel-mounting flange. The purpose of this paper is to describe the methodology and experimental techniques used in determining whether one or both axles failed prior to the accident, and thus contributing to the accident, or whether both axles failed as a result of the rollover and the ensuing impact with the highway. Scanning Electron Microscopy (SEM) technique was used to obtain detailed characteristics of the fracture surface on both axles. Through-thickness hardness profile of the axles was determined using incremental micro-hardness measurements in order to assess the depth of case hardening in both axles. Impact, tensile and fatigue specimens were machined from the remaining parts of the failed axles and were tested to destruction using standard impact (Izod), tensile and fatigue tests. The fracture surface characteristics of the test specimens were compared to those of the failed axles in order to isolate the mode of failure. Based on the results of the above tests, the history of the repair work performed on the rear wheel bearings and the physical evidence of various marks and damages remaining on the vehicle’s body, it was determined that one of the rear axles failed prior to the rollover, while the other occurred as a result of the rollover and ensuing impact with the highway.
Three-Dimensional Analysis of Double Rivet-Row Lap Joints: Part II — Countersunk Rivets
Authors: Iyer K. , Rubin C. A. , Hahn G. T.
Published: November 2021

Three-dimensional finite element analysis of an elastic, double rivet-row, aluminum alloy lap joint with countersunk, aluminum and steel rivets, is presented. Relations between the connection compliance, rivet deformation, peak contact pressures and slip amplitudes, in the absence of interference and clamp-up, are described. Analysis of a connection with non-countersunk rivets is presented in a companion paper. The trends seen in the results are similar to those obtained with non-countersunk rivets, although the peak stress concentrations in the present case are much higher. A superposition approach for estimating stress concentration factors in the panels of multi-row riveted connections with standard or countersunk rivets is presented.
Multiaxial Impact Behavior and Modeling of ABS Polymer
Authors: Saigal A. , Greif R. , Duan Y. , Zimmerman M. A.
Published: November 2021

The multiaxial impact behavior of CYCOLAC GPM5500 (ABS glassy polymer) is obtained as a function of impact velocity and temperature from the standard impact test as specified by ASTM D3763. Finite element analysis (FEA) and ABAQUS/Explicit are used to model the impact behavior of the polymer. The generalized “DSGZ” constitutive model, previously developed by the authors and calibrated using low strain rate uniaxial mechanical test data, is extended to the high strain rate regime and used in the finite element analysis. Load-displacement curves from the finite element analysis are compared with the experimental data and agree well up to the maximum impact load (failure). Therefore, the proposed finite element analysis model can be used to predict the multiaxial impact behaviors of polymers at different temperatures and impact velocities.
Mixed Mode Interfacial Fracture Toughness Evaluation for Flip-Chip Assemblies and CSP Based on Fracture Mechanics Approaches
Authors: Auersperg Jürgen , Kieselstein Eva , Schubert Andreas , Michel Bernd
Published: November 2021

The increasing use of advanced electronic packages like Flip Chips and CSP under harsh environmental conditions, extreme temperatures is often a reason for damage, fatigue and failure of entire components and systems. Consequently, their thermo-mechanical reliability is one of the most important preconditions for adopting these technologies in industrial applications. To prevent chips from being exposed to the external environment integrated circuits are usually encapsulated into packages. As a result, a microelectronic package is basically a compound of several materials with quite different Young’s moduli and thermal expansion coefficients. Additionally, various kinds of inhomogeneity, residual stresses from several steps of the manufacturing process contribute to interface delaminations, chip cracking and fatigue of solder interconnects. This paper intends to describe the investigation of damage and interface delamination phenomena in micro components by numerical investigations by means of fracture mechanics concepts based on nonlinear FEA and experimental investigations. Consequently, the contribution shows the use of non-linear finite element simulations with respect to the nonlinear, temperature and rate dependent behavior of different materials used, the application of fracture mechanics concepts (energy release rate, integral fracture approaches, mode-mixity examinations) in combination with experimental investigations. For these purpose, bending specimens consisting of several materials interfaces widely used in FC ssemblies and CSP have been investigated in particular. In order to evaluate the different approaches used some results have been compared to micrographs from growing interface delaminations by using micro deformation measurements on the basis of a gray scale correlation method applied to micrographs, in particular. The methodology explained is a helpful basis for understanding and evaluating failure mechanisms especially of several polymer material interfaces as well as of solder joints in a more consistent manner. It should support further applications for raising the thermo-mechanical reliability of advanced electronic packages.
Design of a Mortar-Deployed Video Imager
Authors: Condon John A.
Published: November 2021

As part of a US Army Research Laboratory (Aberdeen Proving Ground, MD) project to provide electromechanical packaging support for a developmental gun-hardened, munition-deployed, parachute-deployed video imager, a dynamic FEA structural analysis was performed on the imager’s aluminum housing. This imager can provide real-time, telemetered, digitally-encrypted and encoded video imaging of the battlefield. The housing was designed as a carrier for the power distribution electronics; video encoding electronics; telemetry transmitter and wrap-around antenna; rechargeable NiCad batteries; and CCD camera module, and provided for direct replacement of an existing illumination canister within a modified US Army 120mm mortar system. The imager assembly, once inserted within the mortar body, is first exposed to a launch ‘setback’ acceleration load upon firing and then is exposed to an explosively-generated internal pressure and impact loading upon in-flight fuze initiation, mortar body separation and subsequent imager submunition expulsion. The dynamic analysis entailed verification of the structural integrity and deflections of the imager housing and adjacent impacting steel ‘pusher’ plate under launching, pressure, and impact loadings. A 2-D axi-symmetric, quadrilateral-only, finite element model of the housing and pusher plate was constructed. Contact elements, birth & death displacement constraints and simplified mortar body elements were added to simulate the boundary conditions. Analysis predictions were validated by inspection of the recovered imager hardware following flight testing.
Design of a Human Powered Moonbuggy
Authors: Goforth Emily Kinnaird
Published: November 2021

NASA hosts an annual competition called The Great Moonbuggy Race at Marshall Space Flight Center in Huntsville, Alabama. In the Spring of 2001, the Mechanical Engineering Senior Design Class was divided into three teams and requested to design and build a device for competition. The design criterion was to build a human-powered device capable of carrying one male and one female student across a half mile of simulated lunar terrain. Time was a key criterion as entries were timed on their speed of assembly as well as speed through the course. Other important criteria included safety of the drivers, un-assembled dimensions, inclusion of simulated equipment that an actual moonbuggy would need, and maximum turning radius. The cost of the project had to be within a specified budget of $750. Our moonbuggy, which was constructed under the given budget, survived both runs on the course without any damage. We finished in the top ten of the competition.
Nano-Micro Scale Characterization of Dielectric Materials
Authors: Kohl Paul A. , Allen Sue Ann Bidstrup
Published: November 2021

Thin films of dielectric materials are used as insulating layers in microelectronic systems, including integrated circuits and printed circuit boards. Polymer and spin-on-glasses are widely used as coatings and interlevel dielectrics. The dielectric permitivity and loss are the electrical properties of most interest. However, characterization and optimization of the mechanical properties is essential to the successful implementation and usage of these insulators. In this presentation, thin-film structures for measuring direction-dependent properties (dielectric constant, elastic modulus, and coefficient of thermal expansion), and nano-indentation results on spin-on-glass materials will be presented. Significant improvement in the fracture toughness of nanoporous methylsilsesquioxane glass films has been demonstrated upon introduction of porosity into the films.
Mechanics Issues at Micro-Scale Modeling of Electronic Packages
Authors: Pucha Raghuram V. , Ramakrishna Gnyaneshwar , Sitaraman Suresh K.
Published: November 2021

Due to the temperature dependent material properties and low cycle thermo-mechanical fatigue of electronic packaging interconnects and components, plasticity theories are extensively used to understand their mechanical response in estimating the fatigue life. Experimental evidence indicates that plastic deformation at small scales depends not only on the state variables of stress and strain, but also on their higher order gradients. In this paper mechanics issues related to strain gradient plasticity at micron scale are reviewed through strain gradient enhanced continuum theories. A plastic strain gradient-based approach is employed to study the thermo-mechanical deformation of microvia structure.
Computational and Experimental Study of Laser Microwelding Processes for Electronic Packaging
Authors: Han Wei , Pryputniewicz Ryszard J.
Published: November 2021

Advances in microelectronics depend on reliable packaging. As sizes of components decrease and number of components per package increases, demands on interconnections, or joining, of two parts, e.g., wire to tab, or tab to tab, increase rapidly. Since traditional joining techniques, such as resistance welding, may no longer produce satisfactory microinterconnections, alternative methods are being developed. One of such methods is based on laser microwelding. In this paper, we discuss fundamental processes involved in laser microwelding, outline a computational methodology to simulate thermal effects produced, describe facilities used, present results, and summarize correlations between the experimental and computational data for applications in electronic packaging.