Finite element analysis and experimental whiffletree testing of a small UAV composite wing

The diffusion of design tools suitable for regular lattice structures was recently stimulated by the spread of additive manufacturing technologies that enable the fabrication of complex geometries, exceeding the limits of traditional manufacturing methods. Fillet radii play a fundamental role in the design of lattice materials, reducing the stress concentration and improving fatigue life. However, only simplified beam and 2D models are available in the literature, which are unable to capture the actual stiffness and stress concentrations in the cell nodes of the 3-D beam based lattice structures with fillets. In this paper, four types of polyamide 12 cells, fabricated by selective laser sintering technology, based on cylindrical elements, are studied by finite element (FE) analysis, evaluating the influence of struts and fillet radii on the mechanical properties. In order to study a single cell, specific boundary conditions, simulating the presence of adjacent cells, were adopted in FE analysis. As a result, a model describing mechanical properties as a function of geometrical characteristics is obtained. By this model, it is possible to replace the complex shape of a lattice structure with its boundary, simplifying numerical analyses. This approach, called homogenization, is very useful in the design process of lightweight structures and can be adopted in optimization strategies. Numerical outcomes show that the effect of fillet radius is not negligible, especially in cells having a large number of struts. Moreover, experimental tests were also carried out showing a good agreement with the numerical analysis. Finally, an interactive design process for lattice structures based on experimental and numerical outcomes is proposed.

Seismic behavior and strength capacity of steel coupling beam-to-SRC wall joints

Field investigation and finite element analysis on expansion and shrinkage strains of expansive concrete structures

Objective To explore the establishment of 3D thoracic model by finite element methods, and study the mechanical mechanism of minimally invasive surgery for correcting the chest wall deformity, and provide personalized surgery solution in the future. Methods According to admission and exclusion criteria, we selected 10 cases of pectus carinatum that received chest CT scan. The finite element model of pectus carinatum was established and analyzed by Mimics, ABAQUS, etc. The validity of finite element method for chest wall was verified by comparing the sternal displacement between the simulated values and actual values with the same force. Results The 3D finite element model of pectus carinatum was successfully established and analyzed. The stress distribution of the 10 cases in the posterior ribs was mainly in the 1-6 ribs on both sides, mostly concentrated in the 4th to 6th ribs, and the stress was symmetrical on both sides. Statistical analysis showed that the displacement value of the sternum was correlated, and the validity of the model was verified. Conclusion Mimics, ABAQUS and other finite element modeling and analysis software can effectively establish the thoracic 3D finite element model and mechanical analysis, which can help the further development of personalized minimally invasive surgery for correcting chest wall deformities. Key words: Pectus carinatum; Chest wall deformity; Finite element analysis

In the hot forging process of aluminum piston using water-soluble lubricants, the lubricant layer is often peeled off due to excessive deformation of the material during forming, which may result in direct contact between the material and the die, thereby partially increasing the friction. The constant friction in the Finite element (FE) analysis of this process sometimes results in a completely different result from the actual material flow. Therefore, this study was designed to investigate the friction condition to accurately predict the material flow in the FE analysis. The FE analysis was performed for various material temperatures and friction parameters and the proper friction condition was also derived to remove forging defects. Finally, the forging test was carried out for the initial specimens produced by three different methods to verify the analytical results and eliminate the forging defects. The results showed that the friction depends on the effective strain in the FE analysis and the critical value to increase friction is approximately 1.5–1.8. In addition, among the three different specimens, the shot peened specimen can remove the forging defect by increasing the amount and uniformity of the lubricant on its surface.

This paper describes a new stress-intensity factor (SIF) solution for an internal surface crack in a sphere that expands capabilities for this common pressure vessel geometry. The SIF solution employs the weight function (WF) methodology that enables rapid calculations of SIF values. The WF methodology determines SIF values from the nonlinear stress variations extracted in the uncracked geometry, e.g., from service stresses and/or residual stresses. The current approach supports two degrees of freedom that denote the two crack tips located at the deepest location and the surface of the sphere. The geometric formulation of this solution enforces an elliptical crack front, maintains normality of the crack front with the free surface, avoids non-physical crack shapes with protruding “ears”, and supports two degrees of freedom for fatigue crack growth from an internal crack tip and a surface crack tip. The new SIF solution enables all spherical geometries with the exterior diameter greater than or equal to four times the thickness. This WF SIF solution has been combined with stress variations common for spherical pressures vessels: internal pressure on the interior surface, uniform tension on the crack plane, and bending on the crack plane. These stress variations facilitate solution usability. This work builds on earlier efforts for an external surface crack (PVP2021-61397[1]) and provides a comprehensive solution capability for spheres. This paper provides a complete overview of this solution. We present for the first time the geometric formulation of the crack front that enables the new functionality and set the geometric limits of the solution, e.g., the maximum size and shape of the crack front. The paper discusses the bivariant WF formulation used to define the SIF solution and details the finite element (FE) analyses employed to calibrate terms in the WF formulation. A summary of verification efforts demonstrates the credibility of this solution against independent results from FE analyses. We also compare results of this new solution against independent SIFs computed by FE analyses, legacy SIF solutions, API 579, and FITNET. These comparisons indicate that the new WF solution compares favorably with results from FE analyses. Finally, we summarize the capabilities of this solution in NASGRO®.

A bioengineering course is offered to senior students in the Mechanical Engineering major as an elective at Penn State Behrend in the first semester of their senior year. On average around 20 students enroll in this project-based course and 72% of their grade depends on three comprehensive group projects, one of which is to design a bone plate for a fractured femur. 6% of the grade comes from an individual application presentation, discussing different circumstances in which the concepts in mechanical engineering can be applied to solve/analyze biomedical problems. Background of physiology is introduced in the class while the majority of applicable engineering knowledge was learned in prerequisite courses, such as statics, dynamics, strength of materials, system dynamics, etc. Finite Element Analysis (FEA), an elective offered in both semesters of senior year, is not a prerequisite for this bioengineering course. Most of students enrolled in our bioengineering course either do not have FEA course or are taking FEA concurrently. Therefore in spite of its popularity in the areas related to biomechanics, thus far FEA has not been incorporated in this bioengineering course. Previously, the fractured femur project utilized the applicable theoretical analyses including those from statics, strength of materials, materials, and machine design. In Fall 2015, the instructor of bioengineering course made an effort to have an FEA study on femur and ensuing presentation be completed by a willing student. This student was taking FEA simultaneously with bioengineering, and was scheduled to present during the last week of semester. The instructor of FEA wrote an introductory manual of FEA procedures to analyze a healthy femur using a CAD model of the femur. Then the student used the manual to initiate the FEA study of the fractured femur. A major challenge to the student was the complicated loading and assembly feature of the bone plus the addition of bone plate. After a several week struggle and independent learning, while guided by the faculty members of bioengineering and FEA, the student was able to accomplish the FEA analysis and presented the results to the class. The discrepancy between FEA results and theoretical analysis was shown to be less than 5% in most results. The presentation also included FEA results for a diverse realistic loading and boundary conditions. Since all students had finished the fractured femur project, they actively participated in a meaningful discussion after the presentation. The completion of this project demonstrated the feasibility and importance of incorporating FEA in our bioengineering course. In addition, the presenting student was able to complete a working manual for the FEA analysis of the fractured femur, which can be passed to the future students of this course. A plan is to include FEA in the project as a bonus activity, and regarding the formation of project teams, the instructor would appoint a member who is enrolled in the FEA course. An assignment or project, based on the present FEA study of the femur, can also be incorporated in the FEA course offered at our campus.

Shear connectors are required to build composite (concrete and steel) beams. They are placed at the interface of concrete and steel to transfer shear and normal forces between two structural components. Such composite beams are sensitive to provide structural integrity when exposed to fire as they loss strength, stiffness, and ductility at elevated temperature. The present study is designed to investigate the shear resistance and the failure modes of the headed stud shear connectors at fire exposure and post-fire exposure. The study includes ordinary concrete and concrete with carbon nanotubes (CNTs) to build composite (concrete-steel) beams with structural steel. Experimental push tests were conducted on composite beams at ambient and elevated temperatures, such as 200, 400 & 600℃. Moreover, push tests were performed on the composite beams after being exposed to 200, 400 & 600℃. Push test results illustrated the reduction of ultimate shear capacity and stiffness of headed stud shear connectors as the temperature increased. Although similar values of ultimate shear were obtained for the headed stud connectors in both ordinary and CNT concrete, the CNT modified concrete reduced the concrete spalling and cracking compared to ordinary concrete and was observed to be effective at temperatures greater than 400°C. All specimens showed a lower shear resistance at fire exposures compared to the corresponding post-fire exposures. Moreover, numerical simulation by Finite Element (FE) analyses were carried out at ambient temperature and at fire conditions. The FE analysis results show a good agreement with the experimental results. In the experimental studies, failure of all specimens occurred due to shear failure of headed stud, which was later validated by FE analyses using ABAQUS.

The combination of thin-walled steel structure with concrete infill can be used as the alternative material properties in the building in Indonesia. This composite material is suitable for seismic-resistant building because it has more ductility than conventional material. In the tsunami event, some tsunami debris strikes the building and induced partial or full collapse of the building. The loading tip shape of tsunami debris which contacts to a tubular surface affects the local deformation or buckling mode of the thin-walled structures. In order to investigate the effects, we conducted three-dimensional nonlinear finite element analyses of concrete filled square steel tubular members subjected to concentrated lateral loads by using the finite element analysis (FEM) program MSC Marc/Mentat. The fiber element analysis is also performed to reduce the analysis time of FEM and simplify the analysis. The accuracy of the FEM and fiber element analysis is verified by the experiment. Being based on the parametric numerical study, it discusses the effect of axial load on the load-deflection relations. It shows that the higher the axial load, the more degradation the ductility of the structure.

The operational behavior of a six-phase, 2 poles and 36 stator slot squirrel cage induction machine is analyzed for the effects of stator slot openings in this paper. The study is carried out using the field analysis method and the finite element analysis (FEA) of the two dimensional commercially available finite element QuickField modeling Package. Experimental analysis is conducted on a 1.5 kW machine to validate the integrity of the theoretical method of the original opening slot. The FEA analysis is carried out for no-load (Magnetostatics) and loaded conditions (steady state AC Magnetics). The results show that decreasing the slot opening of the stator winding increases the performance of the machine.

Modern ceramic femoral head components of total hip implants offer improved tribology and wear rates in comparison to traditional bearing materials. However, their brittle nature leaves them susceptible to fracture. As a result, manufacturers test their product lines with experiments designed to prove the mechanical failure strength of these components. These destructive proof tests apply a load to the ceramic samples in a manner that models in vivo conditions. The fracture strength is therefore determined to ensure the implants will withstand physiological loads. Finite element analyses (FEAs) are used to model these experiments and determine the mechanical effects on the heads. The standard method used in these experiments is adequate for new ceramic components, but is undesirable for testing surgically retrieved samples. This test has been recognized to damage the surface of the head's tapered cone which complicates finite element and fracture analysis. The goal of this thesis was to develop a destructive proof test that would minimize taper surface damage by loading ceramic heads in a physiological manner with water pressure, and to create an FEA model of the testing conditions. This concept originated in a patent held by CeramTec GmbH, and was built using a high pressure system that pressurized the inside of ceramic samples until failure. Specifically, this pressure was localized along the region that would be in contact with a metal femoral stem during implantation. The pressure applied to the heads was digitally recorded in ADMET's MTestQuattro software, and was used to select a constant rate of pressure increase. In all, two new alumina components from CeramTec's BIOLOX Forte product line were tested. No retrieval heads were tested, as this experiment was used as a pilot for determining the functionality of the designed experiment. Also, five FEA models were produced to simulate this experiment. Two modeled the conditions experienced by the two new alumina samples, whereas the other models were used for a material comparison. The comparison models were created by applying the maximum possible system pressure to heads made of the three most common ceramic materials: alumina, zirconia (Y-TZP), and zirconia toughened alumina (ZTA). The alumina samples fractured under pressures of 191.86 MPa applied at a rate of 1.96 MPa per second, and 192.60 MPa applied at 1.80 MPa per second. Based on the FEAs, the heads experienced maximum tensile principal stresses of 167.69 MPa and 168.33 MPa respectively. From these stress values, the critical depth for an edge crack to cause material failure along the pressurized region was calculated as 92.41 [mu]m and 91.70 [mu]m. Despite having a significantly lower burst strength than zirconia or ZTA, the two alumina samples required 93% of the test system's pressure capacity to cause failure. The results of the three remaining FEAs displayed similar magnitudes of stress between the modeled materials, and for this reason, no other ceramics were tested. Although there were limitations to this study, the test and FEA performed as required. During the testing procedure, one primary source of error was introduced by the equipment that was used to fixate the ceramic samples. Due to this, the stress values calculated for the fractured heads in the FEAs were likely underestimated. However, the designed test was capable of fracturing ceramic heads in a controlled and repeatable manner without causing significant damage to the surface of the taper. As such, this test should be considered a viable means for evaluating the strength of both new and retrieved ceramic heads.

The present study aimed to identify the optimal design of the unicompartmental femoral component through parameter analysis and stability evaluation. A finite element (FE) analysis was applied to analyse and adjust the parameter combinations of the anterior tilt angle of the posterior condyle resection surface, the position of the peg, the length of the pegand the inclination angle of the peg, resulting in 10 different FE models. Setting three knee flexion angles of 8.4° (maximum load state during walking), 40° (maximum load state during stair climbing)and 90° (maximum load state during squatting exercise), quantitatively analysing the micromotion values of the bone-prosthesis interfaceand defining a weighted scoring formula to evaluate the stability of different FE models. The validity of the FE analysis was verified using the Digital Image Correlation (DIC) device. The errors between the FE analysis and the DIC test at three flexion angles were 5.6%, 1.7%and 11.1%. The 10 different femoral component design models were measured separately. The FE analysis demonstrated that the design with a 0° anterior tilt angle of the posterior condyle resection surface, both pegs placed on the distal resection surface, lengthened 5 mm pegsand a 10° peg inclination angle provided the best stability. The current study proposed a method for evaluating the stability of the femoral component design. The optimal intersurface stability design of the unicompartmental femoral component was achieved with two pegs placed on the distal resection surface, a 5-mm peg length incrementand a 10° peg inclination. These results might provide a reference for the selection of unicompartmental femoral components in clinical practice and therefore improve the survival rate of future unicompartmental knee arthroplasty. Level III.

Investigation of the effects of allogeneic mesenchymal stem cells on bone union and regeneration in the necrosed bone by biomechanical test and the finite element method

ObjectiveDual‐plate fixation was thought to be the gold standard for treating complicated bicondylar tibial plateau fractures, yet it was found to be hard to accommodate the posterior column in three‐column fractures. Currently, column‐specific fixation is becoming more and more recognized, but no comprehensive investigation has been performed to back it up. Therefore, the objective of this study was to validate the importance of posterior column fixation in the three‐column tibial fractures by a finite element (FE) analysis and clinical study.MethodsIn FE analysis, three models were developed: the longitudinal triple‐plate group (LTPG), the oblique triple‐plate group (OTPG), and the dual‐plate group (DPG). Three loading scenarios were simulated. The distribution of the displacement and the equivalent von Mises stress (VMS) in each structure was calculated. The comparative measurements including the maximum posterior column collapse (MPCC), the maximum total displacement of the model (MTD), the maximum VMS of cortical posterior column (MPC‐VMS), and the maximum VMS located on each group of plates and screws (MPS‐VMS). The clinical study evaluated the indicators between the groups with or without the posterior plate, including operation time, blood loss volume, full‐weight bearing period, Hospital for Special Surgery Knee Scoring system (HSS), Rasmussen score, and common postoperative complications.ResultsIn the FE analysis, the MPCC, the MPC‐VMS, and the MTD were detected in much lower amounts in LTPG and OTPG than in DPG. In comparison with DPG, the LTPG and OTPG had larger MPS‐VMS. In the clinical study, 35 cases were included. In the triple‐plate (14) and dual‐plate (21) groups, the operation took 115.6 min and 100.5 min (p < 0.05), respectively. Blood loss in both groups was 287.0 mL and 206.6 mL (p < 0.05), and the full‐weight bearing period was 14.5 weeks and 16.2 weeks (p < 0.05). At the final follow‐up, the HSS score was 85.0 in the triple‐plate group and 77.5 in the dual‐plate (p < 0.05), the Rasmussen score was 24.1 and 21.6 (p < 0.05), there were two cases with reduction loss (9.5%) in the dual‐plate group and one case of superficial incision infection found in the triple‐plate group.ConclusionThe posterior implant was beneficial in optimizing the biomechanical stability and functional outcomes in the three‐column tibial plateau fractures.

A computationally efficient method is proposed for the steady-state performance simulation of brushless permanent-magnet (PM) motors. Only a minimum number of magnetostatic finite-element (FE) analysis (FEA) solutions are used in conjunction with space-time transformations, which are based on the periodicity specific to synchronous machines. For an example electronically controlled interior PM (IPM) motor with six teeth per pole and a distributed winding, a single nonlinear magnetostatic FE solution was employed to estimate the flux density time waveforms in the stator teeth and yoke. Other results include core losses, back electromotive force, and torque. The extension of the method to fractional-slot topologies with reduced number of teeth and concentrated (non-overlapping) coils is discussed with reference to a nine-slot six-pole IPM motor example. The computational time is reduced by one to two orders of magnitude as compared with more laborious time-stepping FEA. Successful validation was performed against experimental data and detailed FEA results.