Investigation on Fragmentation of Pyrophoric Alloy Samples during Taylor Test Using SPH

This study is the first part of a project that aims to assess and model impact-induced energy release (IIER). The present part of the work investigates the failure mode of brittle commercial pyrophoric alloy samples during Taylor impact tests. A series of ferrocerium specimens were shot against tungsten carbide anvils, with velocities ranging between 60 and 140 m/s. A Total Lagrangian SPH model was employed to simulate the deformation and impact-induced fragmentation of the cylinders using LSDYNA®. The modified Johnson-Cook constitutive model was applied in combination with the Cockcroft-Latham fracture criterion. The plastic deformation process, shear cracking, and fragmentation are well reproduced in the numerical results.

Fully and semi-automated shape differentiation in NGSolve

In this paper, we present a framework for automated shape differentiation in the finite element software . Our approach combines the mathematical Lagrangian approach for differentiating PDE-constrained shape functions with the automated differentiation capabilities of . The user can decide which degree of automatisation is required, thus allowing for either a more custom-like or black-box–like behaviour of the software. We discuss the automatic generation of first- and second-order shape derivatives for unconstrained model problems as well as for more realistic problems that are constrained by different types of partial differential equations. We consider linear as well as nonlinear problems and also problems which are posed on surfaces. In numerical experiments, we verify the accuracy of the computed derivatives via a Taylor test. Finally, we present first- and second-order shape optimisation algorithms and illustrate them for several numerical optimisation examples ranging from nonlinear elasticity to Maxwell’s equations.

Hand Function Following Simulated Fusion of Thumb Metacarpophalangeal and Interphalangeal Joints

Background: There is poor understanding regarding functional limitation of thumb strength and dexterity following thumb metacarpophalangeal (MCP) and interphalangeal (IP) arthrodesis. The purpose of this investigation was to quantitatively evaluate the functional limitations of MCP and IP joint fusion using an orthosis to simulate fusion. Methods: Thirty-two healthy volunteers underwent simulated MCP and IP thumb arthrodesis using custom-molded orthoses. Each volunteer was independently assessed for hand and thumb function using the Jebsen-Taylor Hand Function test, lateral pinch strength, tip pinch strength, and Grooved Pegboard test. Comparisons between the 3 groups in all functional tests were carried out. Results: The mean lateral pinch strength was significantly greater in the unsplinted group (8.3 kg) compared with the MCP- (6.3 kg) and IP-splinted (5.7 kg) groups. Mean tip pinch strength was also significantly higher in the unsplinted group than in MCP- and IP-splinted thumbs (4.6 kg vs 4.1 and 3.9 kg). There was no difference in the Jebsen-Taylor or Grooved Pegboard test between the 3 groups. Conclusion: Our study suggests that with a fused MCP joint the lateral and tip pinch strength will decrease by 24% and 10%, respectively, compared with a healthy nonsplinted thumb. A fused IP joint will decrease lateral and tip pinch by 31% and 16%, respectively. This information does not take into account an arthritic thumb. We found that the Jebsen-Taylor test and Grooved Pegboard test were not affected by simulated thumb MCP and IP fusion.

Time Course of Upper Limb Function in Children with Unilateral Cerebral Palsy: A Five-Year Follow-Up Study

Knowledge on long-term evolution of upper limb function in children with unilateral cerebral palsy (CP) is scarce. The objective was to report the five-year evolution in upper limb function and identify factors influencing time trends. Eighty-one children (mean age 9 y and 11 mo, SD 3 y and 3 mo) were assessed at baseline with follow-up after 6 months, 1, and 5 years. Passive range of motion (PROM), tone, muscle, and grip strength were assessed. Activity measurements included Melbourne Assessment, Jebsen-Taylor test, Assisting Hand Assessment (AHA), and ABILHAND-Kids. At 5-year follow-up, PROM (p<0.001) and AHA scores (p<0.001) decreased, whereas an improvement was seen for grip strength (p<0.001), Melbourne Assessment (p=0.003), Jebsen-Taylor test (p<0.001), and ABILHAND-Kids (p<0.001). Age influenced the evolution of AHA scores (p=0.003), with younger children being stable over time, but from 9 years onward, children experienced a decrease in bimanual performance. Manual Ability Classification System (MACS) levels also affected the evolution of AHA scores (p=0.02), with stable scores in MACS I and deterioration in MACS II and III. In conclusion, over 5 years, children with unilateral CP develop more limitations in PROM, and although capacity measures improve, the spontaneous use of the impaired limb in bimanual tasks becomes less effective after the age of 9 years.

Hand Function in Muscular Dystrophies

The aim of this study was to investigate the relationship between Performance of Upper Limb (PUL) and Jebsen–Taylor Test (JTT) to assess and monitor upper limb function progression in patients with muscular dystrophy. Thirty patients diagnosed with Duchenne muscular dystrophy, limb-girdle muscular dystrophy, Becker muscular dystrophy, myotonic dystrophy Type 1, and fascioscapulohumeral dystrophy were submitted to the shoulder, elbow, and wrist domains of PUL, and to JTT subtests. Spearman tests investigated the relationships between PUL and JTT total scores and domains. Correlations were classified as strong ( r ≥ 0.70), moderate (0.40 ≤ r < 0.70), or weak ( r ≤ 0.40). There were strong correlations between the PUL and JTT total scores ( r = −0.706). Although JTT measures time and PUL provides kinesiologic scores, these measures were related. Therefore, muscle synergies, which control the compensatory movements and motor functions involving mainly shoulder, elbow, wrist, and finger movements, are related to timed performance in patients with muscular dystrophies.