Joint Stress Research Articles

Temporomandibular joint stress analysis of patients with different mandibular deformities during unilateral molar occlusion

Mandibular prognathism, retrusion and deviation are common mandibular deformities. They can lead to functional and aesthetic problems due to their important role in the oral system. Different from other occlusions, unilateral molar occlusion often occurs during mastication, which has a deep impact on the functions of temporomandibular joints (TMJs). Therefore, the study of unilateral molar occlusion is of great importance and significance to the daily life of patients with mandibular deformities. A total of 35 individuals were involved in this study, including 11 asymptomatic subjects, 10 patients with mandibular prognathism, 5 patients with mandibular retrusion and 9 patients with mandibular deviation. Finite element (FE) models corresponding to the unilateral molar occlusion were constructed. During unilateral molar occlusion, mandibular deformity increases the pressure on the condyle and articular disc. Compared with mandibular protrusion or retraction, facial asymmetry will significantly increase the stress of TMJ. Chewing on the non-deviated side also will lead to higher stress in the TMJ of patients with mandibular deviation. Therefore, patients with mandibular deviation have the highest risk of temporomandibular disorder (TMD), and it is recommended that patients with mandibular deviation chew bilaterally or with the deviated side.

Structural modification and biomechanical analysis of lumbar disc prosthesis: A finite element study

BackgroundMost ball-in-socket artificial lumbar disc implanted in the spine result in increased hypermobility of the operative level and overloading of the facet joint. MethodsA finite element model was established and validated for the lumbar spine (L1-L5). The structure of the Mobidisc prosthesis was modified, resulting in the development of two new intervertebral disc prostheses, Movcore and Mcopro. The prostheses were implanted into the L3/L4 level to simulate total disc replacement, and the biomechanical properties of the lumbar spine model were analyzed after the operation. FindingsFollowing the implantation of the prostheses, the mobility of operative level, peak stress of lumbar spine models, and peak stress of facet joint increased. The performance of mobility was found to be more similar between Movcore and Mobidisc. The mobility and facet joint peak stress of the Mcopro model decreased progressively with an increase in the Young's modulus of the artificial annulus during flexion, extension, and lateral bending. Among all the models, the Mcopro50 model had the mobility closest to the intact model. It showed a 3% decrease in flexion, equal range of motion in extension, a 9% increase in left lateral bending, a 7% increase in right lateral bending, and a 3% decrease in axial rotation. InterpretationThe feasibility of the new intervertebral disc prostheses, Movcore and Mcopro, has been established. The Mcopro prosthesis, which features an artificial annular structure, offers significant advantages in terms of reduced mobility of the operative level and peak stress of facet joint.

Does spinopelvic alignment affect femoral head cartilage and the proximal femoral physis in slipped capital femoral epiphysis? A finite element analysis

BackgroundSlipped capital femoral epiphysis is a prevalent pediatric hip disorder. Recent studies suggest the spine's sagittal profile may influence the proximal femoral growth plate's slippage, an aspect not extensively explored. This study utilizes finite element analysis to investigate how various spinopelvic alignments affect shear stress and growth plate slip. MethodsA finite element model was developed from CT scans of a healthy adult male lumbar spine, pelvis, and femurs. The model was subjected to various sagittal alignments through reorientation. Simulations of two-leg stance, one-leg stance, walking heel strike, ascending stairs heel strike, and descending stairs heel strike were conducted. Parameters measured included hip joint contact area, stress, and maximum growth plate Tresca (shear) stress. FindingsPosterior pelvic tilt cases indicated larger shear stresses compared to the anterior pelvic tilt variants except in two leg stance. Two leg stance resulted in decreases in the posterior tilted pelvi variants hip contact and growth plate Tresca stress compared to anterior tilted pelvi, however a combination of posterior pelvic tilt and high pelvic incidence indicated larger shear stresses on the growth plate. One leg stance and heal strike resulted in higher shear stress on the growth plate in posterior pelvic tilt variants compared to anterior pelvic tilt, with a combination of posterior pelvic tilt and high pelvic incidence resulting in the largest shear. InterpretationOur findings suggest that posterior pelvic tilt and high pelvic incidence may lead to increased shear stress at the growth plate. Activities performed in patients with these alignments may predispose to biomechanical loading that shears the growth plate, potentially leading to slip.

Mechanical Properties of Folding Arch Frame Joints for Unmanned Arch Erection

The application of folding arch frames is deemed crucial for unmanned arch frame erection, with the selection of the joint form being a determining factor in the overall mechanical performance of the folding arch frame, particularly in influencing the primary support safety. In light of the geological conditions of the New Wushaoling Tunnel project, three feasible joint forms for folding arch frames were proposed: buckle, adhesive, and interference-fit joints. Numerical simulations were conducted to analyze the arch’s overall mechanical and the joints’ local mechanical performances, aiming to identify the optimal joint form. On-site construction data were collected, and the effectiveness of unmanned arch frame erection was evaluated. The design requirements for the vertical displacement results of the steel arches with different joints were met. The maximum shear stress of the buckled arch frame was found to be the lowest, whereas that of the interference-fitted arch frame was the highest. The local shear stress of the adhesive joints was the lowest, while that of the interference-fit joint was the highest. Considering the material application limitations and calculation results, buckle joints are recommended. Unmanned arch frame erection, compared with manual arch frame erection, can save 66.6% of human resources and reduce the construction time by 33.3% to 50%. Statistical analysis has confirmed that the quality of automated arch construction can be guaranteed.

Morphology of polyhedral space habitat modules – Identifying the ideal form using multi-criteria analysis

Over the past fifty years, the form and function of space habitat modules have remained largely unchanged. While cylindrical modules are relatively simple to transport and deploy, their limited size poses a challenge to their efficiency and usability. In contrast, large space habitat construction projects are costly and present logistical difficulties. The development of polyhedral modules could bridge the gap between these two approaches, allowing for modular, polyhedral units to be assembled and linked together to create larger habitats more efficiently and with less risk. However, identifying the most suitable polyhedron for use in space remains a critical question. Previous research has explored the construction of polyhedral modules, but little rigor has been applied to identifying the most optimal form. This is a crucial issue because the first module to be used will likely set the standard for subsequent modules and any disadvantages present at that time will be perpetuated. Therefore, it is essential to identify the optimal form prior to constructing prototypes. This research paper employs multi-criteria decision analysis and sensitivity analysis to compare various candidate polyhedra across several evaluation metrics, including number of faces, volume to surface area ratio, and joint stress, among several other quantitative and qualitative metrics. The results demonstrate that the Rhombic Dodecahedron is a particularly suitable candidate compared to other forms analyzed. Thus, the Rhombic Dodecahedron should be considered the standard polyhedral form for future research involving the development of polyhedral modules.

Study of Panel Zone Behavior in Interior Beam–Column Joints with Reduced Beam Section (RBS)

Based on the post-earthquake investigation of the Beiling and Hanshen earthquakes, many welded rigid beam–column joints were found to exhibit brittle failure. The failure modes of the joint region and the overall steel frame structure under the action of the earthquake need to be studied. The seismic performance of different types of weakened beam-end interior joints was investigated. The finite element method was verified by high-strength steel beam–column joint tests conducted by our research team. Finite element modeling of weakened steel beam flanges and weakened steel beam web joints was carried out based on the validated finite element modeling method. The joints were studied and analyzed using seismic parameters such as joint stress clouds, equivalent story shear–inter-story displacement ratio curves, panel zone bending moment–shear ratio curves, ductility, stiffness, and energy dissipation. The results of this study showed that honeycomb open hole-type joints exhibit a better deformation and energy dissipation capacity compared to open circular web hole-type joints. However, their load carrying capacity is reduced, which is mainly due to the larger area of the web openings. Additionally, double reduced beam section (DRBS) joints exhibit superior seismic performance and plastic hinge outward movement characteristics compared to single reduced beam section (RBS) joints. It was also found that the deformation and energy dissipation of DRBS joints and steel beam honeycomb hole-type joints are mainly borne by the beams, with the panel zone’s participation in energy dissipation accounting for a smaller proportion of the energy.

Joint stress of a hinged platform composed of eight boxes

The box-type hinged platform has important applications in ocean engineering. In this paper, a multi-module assembled box-type platform is described. The mid-section load of the platform is numerically simulated based on the three-dimensional velocity potential theory and the indirect time-domain method through the hydrodynamic module AQWA in ANSYS. The stress of the hinged joints of platforms was performed using finite element analysis software in ANSYS software. The results show that: (1) In irregular waves, the shear force and bending moment in the middle section of the platform increases with the increase of the significant wave height; (2) Under the same towing scheme, the stress of the hinged joints between box platforms shows an increasing trend with the increase of wave level. Under the same wave working condition, the stress at the uniaxial nut of the hinged joints is relatively high, which is prone to fracture.

Microstructure and Mechanical properties of CMT welded AA6063-T6/B4C/ES metal matrix composite using ER5356 filler wire

Aluminium alloy 6063-T6 is a popular choice among different industrial sectors as it portrays various desirable properties like moderate strength, improved corrosion resistance, better weldability and formability etc. These advantages make AA6063-T6 a common choice for matrix in a metal matrix composite. Mostly conventional fusion welding methods like Metal Inert Gas (MIG) and Tungsten Inert Gas (TIG) seem preferable options for welding aluminium and its alloys but it remains a challenge to use them to weld aluminium metal matrix composite. A modified version of MIG i.e. CMT welding, can be explored to overcome the challenges. In this study, an aluminium metal matrix composite has been fabricated with AA6063-T6 as matrix and two reinforcements −one organic, i.e., Eggshell (ES) and one inorganic, i.e., Boron Carbide (B4C), using the conventional stir casting method. CMT welding has been performed on plates cut out from the composites. Microstructure, hardness, tensile strength and residual stress of weld joint of composite have been observed. From micrographs, it is observed that a finer grain has been formed at the Fusion Zone (FZ) in comparison to the Heat Affected Zone (HAZ) and Parent Material (PM). XRD analysis at the fusion line has identified several intermetallic stoichiometric compounds (Al12Mg17, Mg2Si, CaMgSi, CaO, B2O3) and reinforcement B4C and CaCO3 within the matrix volume. The FZ exhibits higher hardness than the HAZ and the PM. Further, the tensile strength of the FZ exceeds that of the unwelded composite due to the presence of metastable strengthening phases of Mg2Si in the FZ, along with reinforcement (B4C and ES) particles. Residual stress analysis reveals tensile stress in the FZ and more compressive stress in the HAZ than in the PM.

Investigation into the effect of deltoid ligament injury on rotational ankle instability using a three-dimensional ankle finite element model.

Injury to the lateral collateral ligament of the ankle may cause ankle instability and, when combined with deltoid ligament (DL) injury, may lead to a more complex situation known as rotational ankle instability (RAI). It is unclear how DL rupture interferes with the mechanical function of an ankle joint with RAI. To study the influence of DL injury on the biomechanical function of the ankle joint. A comprehensive finite element model of an ankle joint, incorporating detailed ligaments, was developed from MRI scans of an adult female. A range of ligament injury scenarios were simulated in the ankle joint model, which was then subjected to a static standing load of 300N and a 1.5Nm internal and external rotation torque. The analysis focused on comparing the distribution and peak values of von Mises stress in the articular cartilages of both the tibia and talus and measuring the talus rotation angle and contact area of the talocrural joint. The dimensions and location of insertion points of ligaments in the finite element ankle model were adopted from previous anatomical research and dissection studies. The anterior drawer distance in the finite element model was within 6.5% of the anatomical range, and the talus tilt angle was within 3% of anatomical results. During static standing, a combined rupture of the anterior talofibular ligament (ATFL) and anterior tibiotalar ligament (ATTL) generates new stress concentrations on the talus cartilage, which markedly increases the joint contact area and stress on the cartilage. During static standing with external rotation, the anterior talofibular ligament and anterior tibiotalar ligament ruptured the ankle's rotational angle by 21.8% compared to an intact joint. In contrast, static standing with internal rotation led to a similar increase in stress and a nearly 2.5 times increase in the talus rotational angle. Injury to the DL altered the stress distribution in the tibiotalar joint and increased the talus rotation angle when subjected to a rotational torque, which may increase the risk of RAI. When treating RAI, it is essential to address not only multi-band DL injuries but also single-band deep DL injuries, especially those affecting the ATTL.

Comparison of Windup and Stretch Pitching Biomechanics in Baseball With Implications for Safety and Performance

Background: Historically, it was assumed by some that high leg lift with windup pitching generated more ball velocity whereas pitching from the stretch was quicker to reduce the risk of base stealing but also more stressful on the arm. However, many now believe that velocity and stress do not differ between windup and stretch and always pitching from the stretch is simpler than mastering 2 techniques. Purpose/Hypothesis: The purpose of this study was to compare windup and stretch fastball pitching biomechanics. It was hypothesized that there would be statistically significant and clinically important differences in ball velocity, timing of angular velocities, joint kinetics, and pitching kinematics. Study Design: Controlled laboratory study. Methods: Fastball pitching biomechanics previously captured for 221 healthy baseball pitchers (105 professional, 52 collegiate, and 64 high school level) were analyzed. For each pitcher, data for 3 to 10 windup trials and 3 to 10 stretch trials were available. Ball velocity was recorded using a radar gun. A 12-camera, 240-Hz automated motion capture system was used to track 39 reflective markers attached to the pitcher. A total of 24 kinematic parameters, 4 temporal parameters, and 5 kinetic parameters were calculated. Data for each parameter were compared across the 2 techniques and 3 competition levels using 2-way repeated-measures analysis of variance (P < .01). Based on previous studies and the expertise of the investigators, the minimal clinically important difference (MCID) was set as 2° for angle measurements, 20 deg/s for angular velocities, 0.5 m/s for fastball velocity, and 0.3% body height × weight for normalized joint torque. Results: Fastball velocity was statistically greater from the windup than stretch for the collegiate subgroup but not for the other 2 levels. The collegiate level difference was below the MCID. Pitching from the windup generated greater front knee height and required more time from initiation of leg lift to front foot contact. From foot contact to ball release, there were 11 additional small, statistically significant differences between windup and stretch; however, each of these was well below the MCID. Conclusion: Pitching from the stretch was quicker and should be used with runners on base to prevent stealing. Pitching from the windup and stretch produced similar ball velocity, joint kinetics, and kinematics. Thus, pitchers may choose to use both techniques or stretch only based on comfort and personal preference. Clinical Relevance: The decision to pitch from both the windup and stretch or only from the stretch should not affect a pitcher's performance or joint stress (and injury risk).

Thermal fatigue life prediction of Ag-2.5Sn solder joint in flip chip

The heat dissipation needs of high-power devices cannot now be met by traditional packing solders due to the fast development of microelectronics interconnect technology. In addition to having outstanding thermal and electrical conductivity, nano-silver-tin paste better satisfies the needs of electronic devices. Studying the thermal reliability of solder joints is extremely important, this article investigates the fatigue life of the nano-silver-tin solder joints in temperature cycling experiments. Based on the life test results, the thermal cycling fatigue life of the nano-silver-tin solder joint is determined to be 2880 cycles. Finite element software was used to replicate the chip’s bonding process and assess the solder joint stress and strain distribution. The stress and strain of nano-silver-tin solder connections under thermal cycling load are accurately modeled using the Anand viscoplastic model and elastic model. The findings indicate that the contact region between the solder connections and copper columns is where the chip generates the most stress and strain. The fatigue life of the solder joint is estimated by using the Coffin–Manson modified equation, and this prediction aligns closely with the experimental results.

Development of a water leakage model test system and investigation of the water leakage behavior in subsea shield tunnels during operation

With the increasing mileage and operation time of China's subsea tunnels, tunnels are entering a period of high disaster. Water leakage is one of the most common disasters. To study the mechanism of water leakage in subsea shield tunnels during the service period, a model test study was carried out by proposing a novel tunnel seepage leakage model test system in this paper. The system consists of a model frame, ground stress loading system, hydraulic pressure loading system, temperature control system, and monitoring system. Through 3D printing, the tunnel segments were innovatively made of resin. The process of uneven settlement, seawater erosion, joint deformation, gasket stress relaxation, and water leakage during the service period were successfully simulated by heating the model segments and local overloading. The test results showed that the joint deformation with service life could be approximately divided into three stages: non-linear rapid growth, linear growth, and non-linear slow growth. And the joint deformation and the aging of the gasket resulted in the decrease of the contact stress of the segment joint. Both exacerbated the leakage in the joint. By the time the service life reaches 16th year, the waterproofing performance no longer met the waterproofing standard for subsea tunnels. The developed test device and method are practical in predicting water surges in subsea tunnels during service life. This paper provides new insights into long-term waterproofing performance testing of shield tunnels under complex conditions.

Multiaxial stress effects on bonding strength in adhesively bonded joints

ABSTRACT This study investigates adhesive bonding as a crucial engineering technique for joining materials, with a focus on load distribution, structural enhancement, and weight reduction. Advances in adhesive formulations, surface preparation, and application techniques continue to expand its capabilities. The research addresses stresses in hybrid joints resulting from pre-tensioning bolts and subsequent axial loading, emphasizing the influence of normal stresses on the critical adhesive-steel interface. Off-axis samples are bonded to mild steel using four different adhesives: SW7240, S370, DP460 (2K-epoxies), and SF479 (2K polyurethane). The choice of adhesive significantly influences shear strength under various loading conditions. Formulating this interaction in terms of maximum shear or von Mises stresses leads to relatively complex failure criteria that make the further analysis dependent on each adhesive. On the other hand, expressing strength at maximum principal stress significantly simplifies comparative analysis, as it consistently exhibits an almost linear trend, indicating strength reduction with increasing hydrostatic pressure for all adhesives, potentially simplifying subsequent strength predictions of hybrid joints.

Experimental Study on Flexural Resistance of UHPC Wet Joint Precast Reinforced Concrete Bridge Deck Slabs with Variable Cross-Section

With the convenient and fast requirements for construction in bridge engineering, prefabricated assembly technology is widely applied in engineering construction. Typically, prefabricated bridge decks are connected through cast-in-place wet joints. Wet joints, as the primary load-bearing parts of bridge decks, undergo complex stress and are prone to cracking and damage. Particularly in the negative bending moment region of bridges, the influence of tensile stress on wet joints is more severe, thus enhancing the mechanical performance and crack resistance of joints becomes crucial. This paper investigates the mechanical behavior of prefabricated reinforced concrete bridge deck panels with variable cross-sections under negative bending moments, focusing on the performance of Ultra High-Performance Concrete (UHPC) wet joints. Full-scale experimental tests were conducted on a 176 m steel truss composite continuous rigid bridge, employing C50 concrete panels with UHPC wet joints. Results show three distinct stages: elastic, crack initiation and propagation, and failure. The maximum failure load reached 822 kN, with a maximum displacement of 21.64 mm. Concrete strains indicate compressive stress near the wet joint and tensile stress near the loading positions. Cracks primarily develop at the wet joint interface and propagate under increasing load, ultimately leading to flexural–shear failure near the variable cross-section of the wet joint. Numerical simulations using ABAQUS/CAE (2020) corroborate experimental findings, closely matching load-displacement curves and identifying damage locations. The study demonstrates that UHPC wet joints significantly enhance crack resistance, meeting design requirements for improved mechanical performance in bridge structures subjected to negative bending moments.

Modulation of Co-depleted zone and shear strength of YG18/40Cr joints by pre-plated Co layer on YG18 surface

The multi-layer composite filler metal (YG18 surface pre-plated with Co layer + Ag–Cu–In–Ti filler metal) was designed in this study. The mechanism of modulation of Co-depleted zone and shear strength of joints by Co plating was elucidated. A more significant Co-rich layer existed around the WC particles, meanwhile, the presence of plastical Ag–Cu–In ternary eutectic between the TiCo layer and the YG18/TiC layer relieved the joint stress and ensured that no cracks were generated in the TiCo layer. Under the condition that the width of the Co-depleted zone was smaller (less than 3 μm), the presence of the dispersed Ti2Cu particles surrounded by the plastic phases ternary eutectic and Cu [s, s] in the filler layer was superior in terms of preventing crack propagation and absorbing the stress concentration. The best modulation of the filler layer microstructure and the Co-depleted zone was achieved when the pre-plated Co layer was around 2.5 μm. The Co-depleted zone was reduced by 50%, and the shear strength of joints was increased by 49% to 291 MPa. The results of the study provide a new way to design new multilayer composite filler metal.

Minimizing residual stress and fatigue crack propagation rate of FSW joints of AA2024-T3 by transient thermal tensioning: Effect of heater distance

Friction stir welding (FSW) is a solid-state welding process that is suitable for joining hardly weldable metals such as aircraft AA2024-T3 aluminum alloy. Despite FSW owns many advantages, however, some problems still arise, especially welding residual stress which influences the weld fatigue performance. In the present work, in-process transient thermal tensioning (TTT) treatment was applied to the FSW process of AA2024-T3 aluminum alloy by putting two symmetrical heaters at the sides of the weld line at distances of 25 mm, 40 mm, and 55 mm. The FSW was conducted at the tool rotational speed of 1500 rpm and tool traveling speed of 30 mm/min whereas the heating temperature was set at 200 °C. Subsequently, changes in microstructure, strength, hardness, residual stress, and fatigue crack propagation rate under TTT treatment were evaluated. The results showed that the use of TTT generated peaks of tensile residual stress along the heater passage which changed the residual stress distributions. It was found that the best fatigue crack propagation resistance of the weld occurred at the heater distance of 25 mm which was attributable to the compressive residual stresses present in the weld region induced by thermal tensioning combined with re-precipitation during welding.

A novel approach of fatigue testing and evaluation of electronic systems based on phase tracking

This paper presents an experimental approach to perform fatigue testing of a lightly damped electronic assembly subjected to harmonic excitation. By leveraging the power of the phase locked loop control algorithm, our proposed work aims to accurately track the phase of the system. This innovative approach enables precise measurement of the drop in resonant frequency due to fatigue, enhancing overall damage prediction. The proposed approach exploits the characteristics of the materials that the phase at the resonance is constant and for a lightly damped system, the value is close to pi/2. In the event that the test article experiences fatigue, and the resonant frequency undergoes a change, the controller will promptly adapt to the new frequency while upholding a constant phase, ensuring the uninterrupted continuity of the testing process. The proposed approach is demonstrated by using the Ball Grid Array (BGA) electronic package as an example, where the test setup, data acquisition, and data monitoring for identifying the interconnect failure are presented. Failure analysis of the test article shows that the primary failure mode is the solder joint failure at the Intermetallic (IMC) layer. A finite element model is developed and correlated with experimental modal analysis to accurately estimate maximum stress and deflection in solder joints. By utilizing the obtained results, one can create a more accurate SN curve for the tested material. This will allow for a better understanding of the material's fatigue behavior and enable more precise predictions of its durability in real-world applications.

Acute effects of negative heel shoes on perceived pain and knee biomechanical characteristics of runners with patellofemoral pain.

To determine the effects of negative heel shoes on perceived pain and knee biomechanical characteristics of runners with patellofemoral pain (PFP) during running. Sixteen runners with PFP ran in negative (-11mm drops) and positive (5mm drops) heel shoes while visual analog scale (VAS) scores, retroreflective markers, and ground reaction force were acquired by applying a 10-cm VAS, infrared motion capture system, and a three-dimensional force plate. Knee moment, patellofemoral joint stress (PFJS), and other biomechanical parameters during the stance phase were calculated based on inverse dynamics and a biomechanical model of the patellofemoral joint. The foot inclination angle, peak PFJS during the stance phase, patellofemoral joint reaction force, knee extension moment, and quadriceps force at the time of peak PFJS of runners with PFP in negative heel shoes were lower than that in positive heel shoes, no significant difference was found in VAS scores, knee flexion angle, patellofemoral contact area, and quadriceps moment arm at the time of peak PFJS. Compared to positive heel shoes, running in negative heel shoes decreases peak PFJS in runners with PFP, which may decrease patellofemoral joint loading, thus reducing the possibility of further development of PFP. Sports Science Experiment Ethics Committee of Beijing Sport University. 2023095H, April 18, 2023 (prospectively registered).

Solder joint shape optimization and thermal-mechanical reliability improvement for microwave RF coaxial connectors

Coaxial connectors are widely used in microwave RF components in wireless communication, aerospace, and other fields. However, the poor interconnection reliability between their inner conductors and circuit boards has been a key factor restricting their development. Thermal cycling and high temperature are the most common working loads for high-frequency devices and the failure generally takes place at the solder joint interface. Therefore this study investigated the solder joints thermal-mechanical reliability of coaxial connectors through a combination of numerical simulation and reliability experiments. Three innovative initial models were used to solve the shape simulation problem of solder joint in planar-curved composite structures. The optimal solder joint shape and structural parameters were obtained through finite element simulation, and the impact mechanism of different parameters on solder joint reliability was explained. After optimization, the maximum stress of the solder joint decreased by 44 % with thermal cycling, while the average stress decreased by 55 %. The reliability tests effectively verified the accuracy of the simulation. In addition, the 150 °C aging tests clarified the kinetics of the growth and evolution of intermetallic compounds in this solder joint structure. The results contribute to the advancement of coaxial connectors solder joints reliability and support the development of more robust and durable interconnects for microwave devices and digital communication systems.

Linking morphology, performance, and habitat utilization: adaptation across biologically relevant ‘levels’ in tamarins

BackgroundBiological adaptation manifests itself at the interface of different biologically relevant ‘levels’, such as ecology, performance, and morphology. Integrated studies at this interface are scarce due to practical difficulties in study design. We present a multilevel analysis, in which we combine evidence from habitat utilization, leaping performance and limb bone morphology of four species of tamarins to elucidate correlations between these ‘levels’.ResultsWe conducted studies of leaping behavior in the field and in a naturalistic park and found significant differences in support use and leaping performance. Leontocebus nigrifrons leaps primarily on vertical, inflexible supports, with vertical body postures, and covers greater leaping distances on average. In contrast, Saguinus midas and S. imperator use vertical and horizontal supports for leaping with a relatively similar frequency. S. mystax is similar to S. midas and S. imperator in the use of supports, but covers greater leaping distances on average, which are nevertheless shorter than those of L. nigrifrons.We assumed these differences to be reflected in the locomotor morphology, too, and compared various morphological features of the long bones of the limbs. According to our performance and habitat utilization data, we expected the long bone morphology of L. nigrifrons to reflect the largest potential for joint torque generation and stress resistance, because we assume longer leaps on vertical supports to exert larger forces on the bones. For S. mystax, based on our performance data, we expected the potential for torque generation to be intermediate between L. nigrifrons and the other two Saguinus species. Surprisingly, we found S. midas and S. imperator having relatively more robust morphological structures as well as relatively larger muscle in-levers, and thus appearing better adapted to the stresses involved in leaping than the other two. ConclusionThis study demonstrates the complex ways in which behavioral and morphological ‘levels’ map onto each other, cautioning against oversimplification of ecological profiles when using large interspecific eco-morphological studies to make adaptive evolutionary inferences.