Mechanical Stress Tests Research Articles

Is there any difference in aortic wall quality between patients with aortic stenosis and those with regurgitation?†

The interaction between aortic valve (AV) and aortic wall pathology is currently unclear. No intraoperative examination or investigation is able to predict postoperative dissection or aneurysm formation in patients operated on for primary AV pathology. The aim of the present study was therefore to evaluate the mechanical and histological properties of the aortic wall in patients operated on for aortic stenosis (AS) or regurgitation (AR). The aortic walls of 229 patients (age 67.5 ± 11.0 years) operated on for AS (n = 135, Group 1) or AR (n = 94, Group 2) were subjected to mechanical stress testing and postoperative histological examination. Ascending aortic diameter was ≥50 mm in 46/229 patients and 40-49 mm in 52/229 patients. AR was associated with an increased tendency to aortic media disruption (P < 0.001) and with media degeneration (P < 0.001) compared with AS patients. The incidence of aortic aneurysm (≥50 mm) was increased in AR patients (35 in AR and 11 in AS, P < 0.01). The aortic wall cohesion was better in patients with an aortic diameter of <40 mm compared with those with moderate dilatation of 40-49 mm (P = 0.009) or an aortic aneurysm (P = 0.002). Our study proves that patients presenting for AV replacement with AR have a poorer quality of the ascending aorta despite a superior thickness compared with patients with AS. In addition, patients with a slightly dilated aorta (40-49 mm) have a poorer cohesion of the aortic wall than those with normal aortic dimensions.

Theoretical model for design and analysis of protectional eyewear

IntroductionProtectional eyewear has to fulfill both mechanical and optical stress tests. To pass those optical tests the surfaces of safety spectacles have to be optimized to minimize optical aberrations. Material and MethodsStarting with the surface data of three measured safety spectacles, a theoretical spectacle model (four spherical surfaces) is recalculated first and then optimized while keeping the front surface unchanged. Next to spherical power, astigmatic power and prism imbalance we used the wavefront error (five different viewing directions) to simulate the optical performance and to optimize the safety spectacle geometries. ResultsAll surfaces were spherical (maximum global deviation ‘peak-to-valley’ between the measured surface and the best-fit sphere: 0.132mm). Except the spherical power of the model Axcont (−0.07m−1) all simulated optical performance before optimization was better than the limits defined by standards. The optimization reduced the wavefront error by 1% to 0.150 λ (Windor/Infield), by 63% to 0.194 λ (Axcont/Bolle) and by 55% to 0.199 λ (2720/3M) without dropping below the measured thickness. ConclusionThe simulated optical performance of spectacle designs could be improved when using a smart optimization. A good optical design counteracts degradation by parameter variation throughout the manufacturing process.

A study on FeCrAl foam as effective catalyst support under thermal and mechanical stresses

Adhesion properties of washcoated γ-Al2O3 layer on FeCrAl metal foams were investigated. For comparison, planar FeCrAl foil was also investigated. Weight gain after washcoating was 19–20wt.% for FeCrAl foams without preoxidation. It was much higher than that of planar FeCrAl foils that went through preoxidation. Thermal shock test with 1000 cyclic heating and cooling up to 700°C showed that long term stability of washcoated γ-Al2O3 layer on FeCrAl foam was also good. Specific surface area of the γ-Al2O3 layer was reduced from 97 to 80m2/g, but weight loss was very low and close to 0%. We attributed this superior thermal property of FeCrAl foam to minimal interfacial force built up by thermal stress at the interface of γ-Al2O3 layer and FeCrAl foam surface. Mechanical stress tests by ultrasonic in petroleum ether solution also showed very good robustness of washcoated γ-Al2O3 layer on FeCrAl foam against the stress with very low weight loss (less than 1%). Such excellent stabilities against thermal and mechanical stresses indicate that FeCrAl foam is a good candidate for catalyst supports under thermally and mechanically harsh environments.

Reliability of Embedded Ultrathin Chips Subjected to Cyclic Stresses

Recently, ultra-thin embedded die technology has garnered much attention for its ability to produce assemblies in two or three dimensions with reduced footprint, low profile, low weight, and conformity. The embedded die technology can be successfully utilized in the development of flexible printed circuits to satisfy the demand for reliable and high density packaging solutions. With tremendous application potential in wearable and disposable electronics, the reliability of the flexible embedded die package is of paramount importance. Presented are results from the experimental study on the electrical performance of ultrathin (≤50 μm) silicon dice embedded into a polymer substrate and bumped using three different techniques—electroplating, wire bonding, and sputtering. The reliability of different packages was evaluated through a series of thermal and mechanical cyclic stress tests. The results suggested that the reliability of all embedded dice was high regardless of the bumping technology. However, compared with the other two methods, wire bonded stud bumps provided better and more consistent performance.

Flexible Multi-Electrode Array for Medical Applications

A flexible multi-electrode array (MEA) with an embedded silicon chip for electrical stimulation of neurons or for recording action potentials has been manufactured and characterized. Possible improvements for medical applications using this novel approach are presented. By connecting and addressing several of these MEAs via a bus system, the number and the density of electrodes can be increased significantly. This is interesting for medical applications such as retinal implants and cochlear implants, and also for deep brain stimulators. Design and fabrication techniques for the multi-electrode array are presented. Finally, first results of mechanical stress tests are shown.

Biomechanical wall properties of human intracranial aneurysms resected following surgical clipping (IRRAs Project)

Background and purpose Individual rupture risk assessment of intracranial aneurysms is a major issue in the clinical management of asymptomatic aneurysms. Aneurysm rupture occurs when wall tension exceeds the strength limit of the wall tissue. At present, aneurysmal wall mechanics are poorly understood and thus, risk assessment involving mechanical properties is inexistent. Aneurysm computational hemodynamics studies make the assumption of rigid walls, an arguable simplification. We therefore aim to assess mechanical properties of ruptured and unruptured intracranial aneurysms in order to provide the foundation for future patient-specific aneurysmal risk assessment. This work also challenges some of the currently held hypotheses in computational flow hemodynamics research. Methods A specific conservation protocol was applied to aneurysmal tissues following clipping and resection in order to preserve their mechanical properties . Sixteen intracranial aneurysms (11 female, 5 male) underwent mechanical uniaxial stress tests under physiological conditions, temperature, and saline isotonic solution. These represented 11 unruptured and 5 ruptured aneurysms. Stress/strain curves were then obtained for each sample, and a fitting algorithm was applied following a 3-parameter ( C 10, C 01, C 11) Mooney–Rivlin hyperelastic model. Each aneurysm was classified according to its biomechanical properties and (un)rupture status. Results Tissue testing demonstrated three main tissue classes: Soft, Rigid, and Intermediate. All unruptured aneurysms presented a more Rigid tissue than ruptured or pre-ruptured aneurysms within each gender subgroup. Wall thickness was not correlated to aneurysmal status (ruptured/unruptured). An Intermediate subgroup of unruptured aneurysms with softer tissue characteristic was identified and correlated with multiple documented risk factors of rupture. Conclusion There is a significant modification in biomechanical properties between ruptured aneurysm, presenting a soft tissue and unruptured aneurysms, presenting a rigid material. This finding strongly supports the idea that a biomechanical risk factor based assessment should be utilized in the to improve the therapeutic decision making.

Arundo donax chipboard based on urea-formaldehyde resin using under 4 mm particles size meets the standard criteria for indoor use

Common reed ( Arundo donax) is a fast growing perennial plant, considered in many countries as a weed or invasive plant. New material developments in recent years have led to common cane proliferation and an invasion in crops and water channels, significantly increasing elimination and control costs. In this study, it is proposed that particleboard be manufactured of common reed ( A. donax). The objective is twofold. On the one hand it allows control of a weed, and secondly, it helps reduce the high dependence of imported wood timber and boards by using a readily and annually renewable resource. The fibers of common reed A. donax, possess high tensile strength (200 N/mm 2 between knots), providing much higher values than wood. This fact together with an important moisture and aging resistance, encourage us to propose it as a suitable raw material for the production of particleboards. In this study we propose the manufacture of particle board with urea formaldehyde resin, which is currently used in the wood chipboard industry. To perform this study, A. donax fibers obtained from a shredding hammer, were classified attending to size and slenderness. Following the standard industrial chipboard manufacturing processes, boards were developed to compare their behaviour against wood chipboards. Fifteen test-tube batches with different proportions of pre-selected fibers were manufactured. New boards were subjected to a mechanical stress test, and other physical properties were also measured. UNE EN—specific wood chipboard regulations were applied. Results showed that particleboard could be manufactured using A. donax adjusting the particle size to a maximum of 4 mm sieves. Finally it can be stated that making common reed panels also involves the reuse of a plant actually considered a weed, to become a raw material for industrial applications, leaving a door open to future development and research areas.

Low-Intensity Pulsed Ultrasound Accelerates Healing in Rat Calcaneus Tendon Injuries

Controlled laboratory study. To evaluate the effect of low-intensity therapeutic ultrasound on the murine calcaneus tendon healing process. Therapeutic ultrasound promotes formation and maturation of scar tissue. Calcaneus tendon tenotomy and tenorrhaphy was performed on 28 Wistar rats. After the procedure, the animals were randomly divided into 2 groups. The animals in the experimental group received a 5-minute ultrasound application, once a day, at a frequency of 1 MHz, a spatial average temporal average intensity of 0.1 W/cm2, and a spatial average intensity of 0.52 W/cm2 at a 16-Hz frequency pulse mode (duty cycle, 20%). Data for the injured side were normalized in relation to the data from the contralateral healthy calcaneus tendon (relative values). The animals in the control group received sham treatment. After a 28-day treatment period, the animals were sacrificed and their tendons surgically removed and subjected to mechanical stress testing. The parameters analyzed were cross-sectional area (mm2), ultimate load (N), tensile strength (MPa), and energy absorption (mJ). A significant difference between groups was found for the relative values of ultimate load and tensile strength. The mean ± SD ultimate load of the control group was -3.5% ± 32.2% compared to 33.3% ± 26.8% for the experimental group (P = .005). The mean tensile strength of the control group was -47.7% ± 19.5% compared to -28.1% ± 24.1% for the experimental group (P = .019). No significant difference was found in cross-sectional area and energy absorption. Low-intensity pulsed ultrasound produced by a conventional therapeutic ultrasound unit can positively influence the calcaneus tendon healing process in rats.

Frequency-controlled wireless shape-memory-alloy microactuators integrated using an electroplating bonding process

This paper reports the wireless control of bulk-micromachined shape-memory-alloy actuators using external radiofrequency magnetic fields and its application to microgrippers. The frequency-sensitive wireless resonant heater to which the gripper actuator is bonded is activated only when the field frequency is tuned to the resonant frequency of the heater. A batch-compatible bonding technique based on photo-defined copper electroplating is developed to mechanically and thermally couple the gripper with the planar heater circuit fabricated using copper-clad polyimide film. The actuation range of 600 μm as the tip opening distance is obtained with normally closed 5-mm long grippers at a device temperature of 92 °C. The field frequency range to which the devices with 140-MHz resonant frequency respond is measured to be ∼13 MHz about the resonant frequency. The manipulation of vertically aligned carbon-nanotube forests is experimentally demonstrated. Mechanical stress tests for the bond formed by the developed electroplating bonding method show a shear strength greater than 40 MPa.

Shaken, Not Stirred: Mechanical Stress Testing of an IgG1 Antibody

Protein aggregation is known to occur under different stress conditions and displays a wide variety of morphologies. In this work, the aggregation behavior of a monoclonal antibody (IgG1) was investigated using two different mechanical stress methods namely stirring and shaking at two temperatures, various fill volumes and headspaces and different amounts of polysorbate present in the formulation. The detection of aggregates in terms of size and number was carried out using various analytical techniques including visible particle inspection, turbidity, sub-visible particle analysis, size exclusion chromatography and dynamic light scattering. The data showed that shaking and stirring resulted in different species of aggregates both qualitatively and quantitatively, where stirring was found more stressful than shaking on the IgG1 formulation. Mechanical stress testing performed at 5 and 25 degrees C only showed a difference on samples stressed by shaking and not by stirring. The headspace in the vials had great influence on the stability of the protein formulation when stressed by shaking. The presence of polysorbate had a protective effect on the antibody, however certain polysorbate concentrations even resulted in increased protein aggregation. An array of analytical methods was essential in order to cover the vast aggregate morphologies, which occurred during agitation.

Thermal, sonochemical, and mechanical behaviors of single crystal [60]fullerene nanotubes

Although related to conventional carbon nanotubes in both shape and construction, fullerene nanowhiskers and fullerene nanotubes have received far less attention. A modified liquid-liquid interfacial precipitation technique is described to produce relatively uniform batches of [60]fullerene nanotubes in high yield. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) reveal that the tubes possess approximately 100-nm inside diameters and 300-nm outside diameters. The [60]fullerene nanotubes degrade slowly at 180 degrees C, eventually collapsing into micron scale [60]fullerene discs and rods, as revealed by optical microscopy and AFM. Ultrasonic cavitation chops [60]fullerene nanotubes into smaller segments within seconds. Longer ultrasonic bathing leads to considerable structural damage in which the sidewalls rupture. Mechanical stress tests using an AFM microscope tip effectively dent and break [60]fullerene nanowhiskers, revealing a hollow interior.

Single-mode small-form-factor fiber optic connectors for enterprise computing systems

Advanced enterprise servers require dense packaging of their fiber optic input/output (I/O) interconnections. This can be accomplished using small-form-factor (SFF) optical connectors and transceivers such as the MT-RJ and LC. Previously, we presented a performance comparison between some of the major types of multimode SFF connectors; at the time, none of these designs was mature enough to offer equivalent performance to established connectors or to support a single-mode interface. We extend the previous work to include recent design enhancements in multimode connectors, as well as the first performance comparison between single-mode SFF connectors. Fiber optic jumper cables are tested using industry standard test procedures and bench marked against the industry standard SC Duplex connector. Initial loss data as well as stress testing are performed. Variations are found in the performance of the connectors types, with the mechanical stress tests of axial and off-axial pull being the most demanding application tests. Because SFF connectors are more susceptible to pull forces, we describe a new type of strain relief developed for high-density I/O interconnects. These connectors demonstrated for the first time design points that are suitable to replace the SC Duplex interface in both multimode and single-mode enterprise system applications.

Lumbosacral Stability of Consolidated Anteroposterior Fusion After Instrumentation Removal Determined by Roentgen Stereophotogrammetric Analysis and Direct Surgical Exploration

The intervertebral stability of bony consolidated anteroposterior lumbosacral spondylodesis is evaluated by roentgen stereophotogrammetric analysis and direct surgical exploration before and after removal of the internal fixator. To determine the remaining in vivo stability of spinal arthrodesis solely retained by a bony integrated carbon fiber cage. Roentgen stereophotogrammetric analysis studies on posterolateral lumbar fusions demonstrate primary spinal stability after additional dorsal instrumentation, which is retained during bony fusion healing. Animal models show a persistent stabilizing effect of the fixator despite the presence of bony fusion. Although direct surgical inspection is the most reliable method to evaluate fused vertebrae, roentgen stereophotogrammetric analysis has also proven to be a highly accurate method to evaluate spinal stability. In 10 patients lumbosacral fusion was performed using carbon interbody implants and an internal fixator. Ten months after initial surgery (range 7-15 months) the internal fixation was removed to reduce local soft tissue impingement as soon as bony fusion was achieved. Fusion site exploration in the course of instrumentation removal was performed by applying distraction, compression, and torque to the grafted area under fluoroscopic control. Any motion indicated a pseudarthrosis. Lumbosacral stability was evaluated by serial roentgen stereophotogrammetric analysis after fusion and after instrumentation removal. During instrumentation removal the mechanical stress test under fluoroscopic control did not indicate pseudarthrosis. After instrumentation removal, roentgen stereophotogrammetric analysis measurements revealed a nonsignificant increase in lumbosacral micromotions within the fused segment with 0.14, 0.31, and 0.44 mm in the transverse, vertical, and sagittal axes, respectively. The internal fixator could be removed without endangering the stability of the fusion. Direct surgical exploration confirmed the adequacy of roentgen stereophotogrammetric analysis as a reliable in vivo method to evaluate lumbosacral stability after anteroposterior fusion.

A novel semiconductor capacitive sensor for a single-chip fingerprint sensor/identifier LSI

We describe a new semiconductor capacitive sensor structure and the fabrication process for a single-chip fingerprint sensor/identifier LSI in which the sensor is stacked on a 0.5-/spl mu/m CMOS LSI. To ascertain the influence of the fabrication process and normal usage on the underlying LSI, sensor chips were subjected to an electrostatic discharge (ESD) test, mechanical stress test, and unsaturated pressure cooker test (USPCT). ESD tolerance is obtained at the value of /spl plusmn/3.0 kV. To investigate mechanical stress, we carried out a tapping test. The sensor is immune to mechanical stress under the condition of 10/sup 4/ taps with the strength of 1 MPa. A multilayer passivation film consisting SiN under polyimide film provides protection against contamination such as water. Thus, under USPCT conditions of 130/spl deg/C, 80% humidity, and 48 h, the chips were not degraded. The tests confirm that the proposed sensor has sufficient reliability for normal identification usage.

Reliability studies μBGA solder joints-effect of Ni-Sn intermetallic compound

This paper studies the bending and vibration effects on the fatigue lifetime of ball grid array (BGA) solder joints. The correlation between the fatigue lifetime of the assembly and the heating factor (Q/sub n/), defined as the integral of the measured temperature over the dwell time above liquidus (183/spl deg/C) in the reflow profile is discussed. Our result shows that the fatigue lifetime of /spl mu/BGA solder-joints firstly increases and then decreases with increasing heating factor. The optimal heating factor Q/sub n/ is found to be 300-680/spl deg/C. In this range, the assembly possesses the greatest fatigue lifetime under various mechanical periodic stress, vibration and bending tests. The cyclic bending cracks always initiate at the point of the acute angle where the solder joint joins the PCB pad, and then propagate in the site between the Ni-Sn intermetallic compound (IMC) layer and the bulk solder. Under the vibration cycling, it is found that the fatigue crack initiates at valleys in the rough surface of the interface of the Ni-Sn IMC with the bulk solder. Then it propagates mostly near the Ni-Sn IMC layer and occasionally in the IMC layer or along the IMC/nickel interface. Evidently, the Ni-Sn IMC contributes mainly to the fatigue failure of the /spl mu/BGA solder joints. The SEM and EDX inspection show that only Ni/sub 3/Sn/sub 4/ IMC forms between the tin-based solder and the nickel substrate. Moreover, no brittle AuSn/sub 4/ is formed since all the Au coated on the pad surface is dissolved into the solder joint during reflowing. The formation of the Ni/sub 3/Sn/sub 4/ IMC during soldering ensures a good metallurgical bond between the solder and the substrate. However, a thick Ni-Sn IMC influences the joint strength, which results in mechanical failure. Based on the observed relationship of the fatigue lifetime with Ni-Sn IMC thickness and Q/sub n/, the reflow profile should be controlled with caution in order to optimize the soldering performance.

Performance comparison of small form factor fiber optic connectors

A comparison of small form factor (SFF) fiber optic connectors is presented for LC, MT-RJ, SC-DC, and VF-45. Multimode jumper cables were tested using industry standard test procedures and bench marked against the industry standard SC Duplex connector. Initial loss data as well as stress testing was performed. Variations were found in the performance of the connectors types and between connectors of the same type from different suppliers. In some cases the connectors out performed the SC Duplex on some tests but no connectors out performed the SC Duplex on all tests with the mechanical stress tests of axial and off-axial pull being the most difficult to exceed. These connectors are rapidly developing and are at different levels of maturity but none of them tested out to be a fully mature replacement for the SC Duplex connector yet.

Design and evaluation of coils for a 50 mm diameter induction coilgun launcher

Coilguns have the ability to provide magnetic pressure to projectiles which results in near constant acceleration. The authors have developed coils to produce an effective projectile base pressure of 100 MPa (1 kbar) as a step toward reaching base pressures of 200 MPa. The design uses a scalable technology applicable to the entire range of breech to muzzle coils of a multi-stage launcher. This paper presents the design of capacitor-driven coils for launching nominal 50 mm, 350 g projectiles. Design criteria, constraints, mechanical stress analysis, launcher performance, and test results are discussed. >

Case Studies in Quality and Reliability Analysis of Fine Pitch Solder Joints

Rapid feedback on the effect of changes in materials or assembly process parameters on solder joint quality is essential in process optimisation for fine pitch surface mount solder assembly. This is particularly the case where the demands of high volume production do not allow lengthy experimentation to be carried out on the production line. The greater precision and care required in analysis of fine pitch solder joints places a further constraint on the speed at which the analysis can be carried out. The techniques of microstructural analysis, solder joint mechanical strength testing and short duration environmental stress testing must be used to meet a rapid turnaround quality and reliability analysis requirement and to maximise the amount of information obtained from each stage of the analysis. Three case studies are detailed which demonstrate the use of these techniques in a high volume production context to provide rapid feedback on joint quality. The case studies have been selected for presentation not only to demonstrate the analysis techniques but also because they address issues which are of current interest due to the increased usage of fine pitch packages in production and the constraints on the use of solvents for cleaning of circuit boards. The studies are:

The polarimeter and its practical applications

A review of those fundamental facts and relations concerning polarized light with which the reader should be familiar is given. The devices which serve as the polarization elements of all instruments are then described, followed by a description of half-shade azimuth polarimeters, elliptic polarimeters, Tool's general polarimeter, and a Universal polarimeter designed at the Bureau of Standards. The practical applications of polarimeters to saccharimetry, photometry, colorimetry, pyrometry, determination of the optical constants of absorbing media, mechanical stress analysis and testing of the optical homogeneity of glass are all briefly described.