Program slicing is an effective technique for narrowing the focus of attention to the relevant parts of a program during the debugging process. However, imprecision is a problem in static slices, since they are based on all possible executions that reach a given program point rather than the specific execution under which the program is being debugged. Dynamic slices, based on the specific execution being debugged, are precise but incur high run-time overhead due to the tracing information that is collected during the program's execution. We present a hybrid slicing technique that integrates dynamic information from a specific execution into a static slice analysis. The hybrid slice produced is more precise than the static slice and less costly than the dynamic slice. The technique exploits dynamic information that is readily available during debugging-namely, breakpoint information and the dynamic call graph. This information is integrated into a static slicing analysis to more accurately estimate the potential paths taken by the program. The breakpoints and call/return points, used as reference points, divide the execution path into intervals. By associating each statement in the slice with an execution interval, hybrid slicing provides information as to when a statement was encountered during execution. Another attractive feature of our approach is that it allows the user to control the cost of hybrid slicing by limiting the amount of dynamic information used in computing the slice. We implemented the hybrid slicing technique to demonstrate the feasibility of our approach.

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The research in this article entails the design of materials systems and tunable energy absorbing properties respond to a range of energy absorption needs in different impact conditions. Tunable energy absorption of bilayer cellular foams is investigated using hollow glass spheres with different wall thickness and densities. Co‐cured bilayer foams are prepared through sintering of the spheres, and their microstructures and mechanical responses to quasistatic uniaxial compression are investigated. Co‐cured system exploits localized voids density (>50 μm) locally at the interface which is induced via different shrinkage rate of spheres, leveraging tunable energy absorptions. Mechanical testing shows that the voids at the interface lead in the sequential collapse of the layers, resulting in a distinctive two‐step stress–strain profile. For comparison, bilayer samples are fabricated using epoxy. These samples show a different mechanical response from the co‐cured sample by not showing the two‐step stress–strain. The co‐cured samples exhibit 14.8% more specific energy absorption than epoxy bonded samples. The results suggest that co‐cured samples can limit impact stress and achieve a higher energy absorption capacity than epoxy bonded samples. The manufacturing concept and system design expand the capabilities of cellular foams, yielding desired energy absorbing properties in a diverse range of applications.

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Energy-absorbing materials have extensive applications in aerospace and automotive applications. Research has shown buckling initiators, or triggers, in energy-absorbing tubular structures increase the energy absorbed by encouraging the side panels to fold when loaded out of plane in compression conditions. Additively manufactured TPE honeycombs were designed in this study to include these buckling initiators, which introduced a slight decrease in initial weight, as well as initial stress concentrations, while improving crashworthiness characteristics. The samples with buckling initiators (1BI) showed an increase in crush efficiency when directly compared to their no buckling initiator (0BI) counterparts. The 1BI samples maintained an increased crush efficiency regardless of the strain rate used. The samples with 1BI were able to better equilibrate the peak stress with the plateau stress. These honeycomb samples were found to maintain their crush efficiency, even after multiple rounds of compression testing. The quasi-static 0BI samples experienced a 23.4% decrease in the peak stress after multiple rounds of compression testing, while the 1BI samples saw approximately a 23.0% decrease. The 1BI samples averaged a decrease in crush efficiency of 0.5%, while the 0BI samples saw a decrease in crush efficiency of 5%. As the strain rate increased, the crush efficiency for the 1BI samples showed an increase in performance, with a smaller degradation in crush efficiency over multiple uses. Visco-elastic honeycomb with buckling initiators has a higher energy absorption than samples with no buckling initiators when exposed to multiple impact cycles.

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The research in this paper entails the design of material systems with tunable energy-absorbing properties. Hollow glass microspheres of different densities are layered using dry powder printing and subsequently sintered to form a cellular structure. The tunability of the bilayer foams is investigated using various combinations of hollow microspheres with different densities and different thickness ratios of the layers. The mechanical responses to quasi-static uniaxial compression of the bilayer foams are also investigated. These bilayer samples show different mechanical responses from uniform samples with a distinctive two-step stress–strain profile that includes a first and second plateau stress. The strain where the second plateau starts can be tuned by adjusting the thickness ratio of the two layers. The resulting tunable stress–strain profile demonstrates tunable energy absorption. The tunability is found to be more significant if the density values of each layer differ largely. For comparison, bilayer samples are fabricated using epoxy at the interface instead of a sintering process and a different mechanical response is shown from a sintered sample with the different stress–strain profile. Designing the layered foams allows tuning of the stress–strain profile, enabling desired energy-absorbing properties which are critical in diverse impact conditions.